This is the answer to your question of why believers keep believing. It is for the same reason that there is something rather than nothing. This fact alone is The Mystery, and is a fact that anyone can verify. Your question might really be... why is there evil in the world? And, I guess the answer to that is also the same. The answer, you see, really just creates more questions. The fact is, this something rather than nothing has been in existence by itself for an eternity, and was never created or evolved. And, it isn't just "something", that would be misleading. It is everything. This is a very difficult concept to comprehend at first. And, how do I know this, you might ask? I know this because I am a part of it,I am alive, and I can communicate with it both internally and externally. It also teaches me, because I want to be taught and I make an effort to learn.

I am not in the slightest bit religious, though.