For the same reason you do.

Okay, say you have an ant farm or something like that. You have the power to pour bleach in your ant farm and kill all of them at once. Or you could drop food in there. They are aware of you and think of you like a god, so they worship you. But when they do shitty things to each other, they wonder why you didn't step in and intervene. You qualify as all-powerful and all-knowing (imagine you can see all the pathways from both sides), so, why don't you step in? The fact is, you don't really care. You might care that you have an ant farm. You care about the bigger picture. But the small things? Like who gets to be queen and the shitty things they do to each other? It's not really your concern.

If a god were a real thing, it would be some kind of life force that is quite beyond our understanding, and thus, it wouldn't really care about our internal struggles, if it had a motivation to see us as a species succeed (in what? just surviving? Basically).

It's easy to say gods don't exist, but, we really don't know what's out there in the stars. Imagine something could live in space without oxygen, and imagine it can't be seen by our instruments. That might be like a god. We don't really know.