I wouldn't say that, no
No, I'd say you are a coward without the courage of your convictions. I was a weak atheist when I was younger. I felt that there was no God but had a traumatic experience and did indeed turn to God. Afterwards, I considered my actions and reviewed my beliefs. Since that day no situation has called to me go back on my beliefs. Honesty is important, regardless of not knowing the reality 100%.
Why would a crisis make me... *sees your username*... DEAR GOD! PLEASE DON'T LET HIM KILL ME!! XD
A lot of people don't actually reject the belief in Gods existence. They reject the teachings of God and Gods authority over them. They sometimes call themselves atheists but it is an act, they just hate God. But when the shite hits the fan and they are in a desperate position they will quickly forget about their ob<x>jections and pray out of desperation.
No, plenty of people reject the various god claims, us atheists reject them all. Do you just hate Zeus or reject the idea Zeus is real? Seriously...
There are some true atheists out there but they are rare. Yes some reject all concepts of God because the thought of a God over and above them who is unreachably superior to them is offensive to them. They disagree with the very concept of God because they want to be their own God.
If that ever happens it's probably desperation - a bit like death row criminals finding God, for example, although hopefully far less extreme in most cases.
Praying is as natural as wishing. People will often cry out to the god they have heard the most about in a time of crisis (which will vary depending on where they live and what era), but I wouldn't say they believed in that religion, merely that they were desperate and vulnerable.
I think you are asking why humans can't simply be rational about everything? The world is a scary place, personally I can think of good arguments why a truly rational person wouldn't even consider this world worth living in - perhaps a bit of irrationality is passed down to each of us as a survival trait.