> religious clergy who doesn't believe in God but has no choice

In what sense they don't have a choice? Catholic church won't kill you if you quit.

First, you can leave the religion entirely, then they have no power over you. Second, you can quit your job while staying in the church (as Pope Benedict did), and I think you probably can quit priesthood... but if even you couldn't, quitting the religion is always the Plan B.

So I suspect that the main reason for staying is that getting paid for talking BS is just too convenient. Not believing in God, but preaching to people who believe in God and believe that you are the speaker of the God.