Whatever reason it takes I guess.
.
To me this is asking why does grass grow.

The same reason there are billions of other planets and stars populating the universe: science.

We are here to do our own small part in helping the human race to answer the question you just asked.

We are here I believe, because Aliens planted us here. I believe Aliens were our beginning rather than the biblical god stories.

because consciousness needed a host.

I believe we are here to make a difference. Every little effort helps.

Because amino acids combined into complex proteins.

42

We're here because we're here because we're here.

Because. Duh.

And what are you doing over there? Hey you! Get away from that...

The purpose of life is to beget more life.

Life goes against the probabilistic direction of increasing entropy in the cosmos. Information is the mathematical negative of entropy(Shannon). Genetic code is the information that defines an organism. Mixing that information begets baby organisms(more life)

Our mind/spirit/emotion/psychology is our conscious life which contains orders of magnitude more information than our genetic code. Mixing our consciousness through conversation/bonding/love mixes the information in our consciousnesses and begets consciousness babies e.g.social constructs, languages, traditions, memes, cultures, tribal knowledge, etc.

That would be a philosophical or theologian question. “Why are we here?” Is not an objective question. How do you quantify it? I don’t see that there is no “why” or deeper “meaning” to life. Life is what you make it, you make your own meaning to your individual life. Or maybe as a famous Poet put it: “O Me! O life!... of the questions of these recurring; Of the endless trains of the faithless—of cities fill’d with the foolish; Of myself forever reproaching myself, (for who more foolish than I, and who more faithless?) Of eyes that vainly crave the light—of the objects mean—of the struggle ever renew’d; Of the poor results of all—of the plodding and sordid crowds I see around me; Of the empty and useless years of the rest—with the rest me intertwined; The question, O me! so sad, recurring—What good amid these, O me, O life? Answer. That you are here—that life exists, and identity; That the powerful play goes on, and you will contribute a verse.” Walt Whitman

"We" are here because if it were only "Me" I might get lonely having only the birds, beasts, and fishes to converse with. Not that they do not make fine and enjoyable companions, but their somewhat rudimentary vocabularies render them rather poor conversationalists in matters of physics and philosophy which interest me. Also, I have come to appreciate and find pleasure in the musical and artistic creations of my fellow human beings, so I am content to share a bit of my vast Universe with them.