Science is agnostic. It makes no statements about God, gods or Non-gods. Science doesn't need to place value on anything. Atheists don't own science and science is not a religion. By trying to make it the Atheists' religious thing, Science becomes weakened and non-credible.
Don't anthropomorphize science. It hates that.
You're absolutely right that science doesn't need to place value on anything. Science is a process, a methodology and, to a lesser extent, a culture. It doesn't have needs. And yet besides being completely right, you also completely miss the point.
Science doesn't need anything, atheism doesn't need anything... but people do need something. People find the emotionless, purely rational "Spock" view of science deeply unfulfilling (ignoring for the moment that spock wasn't wholly rational or emotionless, and neither was Data, even without his emotion chip), and therefore they seek something else, something more, something, in fact, bigger than themselves which (somewhat paradoxically) gives value to them and makes them more than just "chemical scum on the surface of a typical planet", as Hawking put it. Otherwise, what's the point? Different people feel this need in varying degrees, and atheists tend to be people who are towards the less "needy" end of that particular spectrum (which doesn't make them superior or inferior).
Atheists who see religion as a problem to be solved, and wish to convince people to stop seeking gods find this need for something in their religious fellows to be an obstacle... because the atheists have nothing to offer to fill that human need. At least, that's the argument.
I recently read a book which I think has an excellent answer to this. The book is "The Beginning of Infinity", by David Deutsch, and in it Deutsch makes a compelling argument that, rather than being irrelevant chemical scum, people (a term which Deutsch defines, and of which humans are the only example we know) are objectively the single most significant phenomenon in the universe (actually, the multiverse, since Deuetsch is a proponent of the many-worlds hypothesis). The reason we're so incredibly important not only provides value but also purpose, and I think that value and purpose can fill the need.
Deutsch argues that the reason humans have become people and therefore important is because we've made "the jump to universality", by which Deutsch means that we have become "universal explainers", capable of developing an infinite stream of ever-better and ever-more-detailed explanations of how the universe works, and therefore also "universal constructors", capable ultimately (given the necessary knowledge, which we have the capacity to obtain) of constructing anything which is not physically impossible (note that universal construction also implies the ability to overcome any inherent deficits in our brains that might impose limits on our capacity as universal explainers).
As to how those characteristics make us the most important phenomena in the universe, Deutsch provides several examples. I'll relate two of them. First, he points out that we believe -- with reason -- that if there are other people in the universe it is highly likely that we will be able to detect them, even if they're hundreds, thousands or millions of light years away. This belief is the rationale for the SETI project, and it is based on the simple observation that people, when they become radio engineers, produce signals which are distinguishable from any phenomenon that exists in a universe without people. More succinctly, people are one of few phenomena which can be detected over interstellar distances. This puts people in a class of cosmic significance that at least rivals that of stars.
Second, he points out that as universal constructors, who can ultimately create any arrangement of matter and energy which is not prohibited by the laws of physics, once we learn how, that we're actually more significant than stars, supernovae, quasars, etc. It's conceivable that we will someday learn how to harness and modify those vast phenomena, for example we may someday wish to prevent a supernova and do so by removing enough mass from the star to prevent it. We don't know how to do that, of course, but we already know exactly what would have to be done, exactly how much mass would have to be removed from a given star, and by when.
Further, if we consider the set of all possible arrangements of matter and energy in the universe and then consider which of them could occur via the operation of the laws of physics in the absence of people, vs which could occur in the presence of people (universal constructors), we see that only a vanishingly small set of states is possible without people. The classic example is that of Paley's "pocket watch on the heath"... what is the probability that in the absence of people that a pocket watch would come into existence? The watch's structure is not only intricate, it is all geared toward the purpose of telling time. It's extremely unlikely that that arrangement of atoms could occur by chance. Of course, the same argument can be applied to our own bodies, but we do have an explanation for how they could occur by chance.
So, the cosmic significance and importance of people, as universal explainers and constructors, clearly fulfills our human need to be significant. We, collectively (including other non-human people), are the most significant and powerful thing in the universe. But how does that address the need for a purpose larger than ourselves? The purpose is to achieve our destiny, of creating that infinite stream of knowledge, and of applying it to better the existence of people. In a word, progress, making people, collectively and individually, happier, smarter, better, freer, more powerful, etc. through developing ever-richer explanations of the universe we inhabit -- and create.
Note that this still leaves open the question of how to create and justify morality, something that normal people feel is important, and another key role of religion that atheists sometimes have a hard time replacing. Relativist, or amoralist philosophies abound, and can be logically very consistent, but are almost universally unappealing to people. Deutsch takes a stab at that, too, arguing that morality is also objective and can be derived from the laws of nature (physics). His arguments there are interesting but not quite as compelling.
(Disclaimer: Note that I am not an atheist. I do believe in God, and believe that He is our creator and the creator of the universe we inhabit. However, I find objective arguments of humanity's importance and morality's fundamental nature very interesting, and not in the slightest in conflict with my view of a benificent creator who wants us to find fulfillment in our struggles to progress.)