You are looking at rather biased numbers. The most comprehensive recent survey on religious belief among scientists was done in 2009 by the Pew Research Institute. This was a large survey and is MUCH more reliable that this supposed 7% of “greater” scientists who believe in God. I am sure this “survey” of scientists is not scientific! In the 20009 survey 51% of professional scientists said they had some sort of belief in a supernatural reality of any sort and 33% said that they believe in something like biblical theism. My experience tells me that the majority of physicists have some sort of belief in the supernatural, somewhat over half of chemists do, but significantly less than half of biologists and neuroscientists have some sort of belief in God. My experience tells me that biologists and neuroscientists tend to self-select as unbelievers because the world views of evolution and materialism tends to keep believers away from this area, whereas in physics, where the fine tuning of the physical world is so obvious, relatively few physicists are able to maintain a strict atheist view. In my own chemistry department from which I recently retired, of the seven full-time faculty, four were Christians of some sort, one was Jewish but an unbeliever and two were atheist or agnostic. This is typical.
Of course, if we go farther back in time, all scientists (and I mean literally all) were believers in the sixteenth through eighteenth centuries, and the great majority were in the nineteenth century. In fact, early science (natural philosophy) was considered a branch of theology–the study of general revelation in nature.
Now it is time for me to answer your question. Although the numbers you have heard are negatively biased, it still is true that, on average, considerably less scientists believe in God than the general population. Why is that? I believe that there are a couple of reasons. One of these is that atheists and agnostics tend to self-select into the science fields. A person who believes that the only things which are real are physical, measurable things (which is virtually the definition of atheism) is naturally going to self-select into a field of study which, at least on the surface, tends toward this way of thinking. Let me explain what science is and what scientists do which will explain the reason for this bias. I am a scientist and I, obviously, believe that God is Creator, that he can and does work miracles and that all of nature is the direct result of the creative work of a theistic God. However, when I work as a scientist, it is my “job” to only discuss those things which are “natural.” In other words, the only sphere of study for scientists is the things which occur in our universe which happen due to natural law. For this reason, the supernatural is ruled out of consideration in doing experiments and in developing scientific explanations of things. Science rules out the supernatural in its explanations a-priori. This does not mean that scientists as individual human beings rule out theism in their own belief systems, but that when scientists “do” science they rule out supernatural explanation our of hand in the activity.
Because science as an activity rules out consideration of the supernatural when “doing” science, those who have a non-theistic world view tend to be scientists. What I am saying is that science does not produce atheists but atheism produces scientists. Atheists do not tend to be social workers. They do not tend to be doctors or nurses. They do not tend to be car salespeople, but they do tend to be scientists. This is the principle reason that scientists considerably over-represent the number of atheists in our society as a whole. Was it their study of science that made them atheists/agnostics or was it their atheism/agnosticism that made them study science? I say that it is the latter of the two in the vast majority of cases.
I am convinced that the evidence produced by science VERY strongly supports belief in God. The fine-tuning of the fundamental constants, the obviously designed nature of the properties of water, the level of organization in all life and much, much more in the natural world strongly points to the existence of an intelligent designer and creator. That is what I am convinced of. Nevertheless, science as an activity is “friendly” to those who have an atheistic or naturalistic worldview, and this explains why so many with this worldview tend toward science. It is reasonable to ask why, if the evidence from science is so strongly supportive of theism, then why do not more scientists come over into the theism camp once they go deeply into science.? This a reasonable question, and it deserves an answer. My opinion is that the problem here is that the majority of atheists think presuppositionally in this area. In other words, they look at the world through a naturalistic lens. This worldview determines how they interpret the data, not the data itself.
I am sure you do not believe that the majority vote equals truth. Maybe you think of scientists as smarter-than-average so their votes get extra weight. I am not sure why you are so concerned with the opinions of scientists, as opposed to engineers or lawyers or psychologists and the like. I am not in the least intimidated by scientists who happen to be unbelievers. To me, they are obviously wrong. Their explanation of the evidence about the world is completely unable to explain the existence of the universe, of life and of many, many other things. I am not intimidated by these atheists, but I feel sorry for them, as they miss the beauty of creation which is right before their eyes. Why do they cling to this naturalistic idolatry? Romans 1:18-23 suggests a possible reason, which is that they choose to ignore the obvious because they do not want to believe. This may be the case, but every agnostic and every atheists is an individual and the reasons they land in this place may vary much. Perhaps you can do some of your own research and ask some of your scientist friends–both theists and non-theists–why they have the world view that they have.
You suggest that there may be “cultural” reasons for atheism being relatively high in science. This is an interesting idea to pursue. In modern, Western societies, there has been a commitment to the assumption that human reasoning can answer many if not all questions. In such a cultural setting, there is a bias toward naturalistic explanation rather than supernatural explanation. The modernist, Western culture does tend to produce unbelief to some extent. It will be interesting to watch in the next generation or so what the postmodern world does in terms of creating more or less agnosticism. Statisticians tell us that postmodernism tends to produce “nones.” These are people who see themselves as spiritual in the broadest sense of the word, but who do not commit to any particular religious worldview. This being the case, it is likely that atheism will not dramatically increase in the next generation or so, but commitment to established religions may continue to decline. Of course, as a reminder, what our culture is doing has virtually no connection with whether the existence of God is “true” or not. Opinion does not equal truth and cultural trends to not equal truth. This is rather obvious, is it not?