My curiosity is, what leads people to spend time and effort to analyze millions of universe pictures to identify stars without any specific reward (they can't even name new discoveries)?
This may sound like a cliche, but the discovery is the reward. Everything else is just icing on the cake, may make your life more comfortable, may make you feel appreciated, but it's optional. I mean, your question actually says "why would anyone do any science?", because have in mind that doing fundamental science is not that lucrative in terms of pay compared to the value it brings, and only a vanishingly small percentage of scientists actually get some kind of a recognition, and of those who do a vanishingly small percentage is even mentioned to general public.