Why are there so many stars in the universe? Do they help us humans in any way?
See explanation for a few (slightly rambling) thoughts...
This question seems curious to me in the way that it is asked. Given that there are so many galaxies in the universe, let alone individual stars, does it not make our world, solar system and galaxy appear inconceivably tiny compared with the whole universe. So why are we wondering, ok so what use are all these stars to man? Should we instead be asking what purpose the universe has for us, tiny and apparently insignificant as we seem to be?
Firstly, I guess that I should remark that many of the rarer heavier elements on Earth, upon which our existence depends, are from supernovae - i.e. the remains of stars now long gone, that underwent cataclysmic explosion at the end of their lives. So in some sense, we humans are more dependent on other stars that have gone before than on stars (apart from our sun) which still shine today.
Historically, the birth of our Sun was possible due to a concentration of gases by and in the Milky Way Galaxy, the galaxy having grown for several billion years before our sun was born. Such a concentration was almost certainly made possible due to the other stars and material in our galaxy, and contained heavier elements from supernovae from earlier stars, as already remarked. Earlier stars in our galaxy would consist mostly of lighter gases: hydrogen and helium, with less opportunity for rocky planets like our Earth to form around them, whereas our sun and planets had a richer mix of elements to work with.
A more fundamental question is why does there appear to be far more matter than antimatter in the universe? If matter was created from pure energy then we would expect an equal quantity of matter and antimatter. This is one of the great unsolved mysteries - an apparent, unaccounted for, asymmetry between matter and antimatter.