Firstly, that’s what Jesus did.

Also, we all have our own relationships with God. In a relationship, one person doesn’t always do all the work, right? If you do the work and give to God, he’ll give so much back to you.
If God existed as an undeniable presence (though I think he does to me), then yeah, like was said, there wouldn’t be anything to faith. He does exist as this undeniable presence, but I think that’s only if you’re willing to do the work to hear him. He’s not always so loud.
A quick final note–if he existed as an easily proven, seen, and believed entity, people wouldn’t be able to deny it. On one hand, in an increasingly secular culture, this might sound great. But it doesn’t give people the chance to say no–it’d be like me walking up to you and saying I don’t believe you exist. It’d just be silly. You can’t say yes unless you’re entirely free to say no.