For Christians, its basically the one job we're given by a guy that created an infinite and expanding universe from nothingness.
Matthew 28:16-20
Furthermore, if you honestly believed you'd found the answer to life's questions (in addition to a way to avoid an eternity of torment) wouldn't you want to share it? Frankly if religious people DON'T share their faith, that seems like a bit of a dick move to me ... they get to go to paradise, but because they're lazy or whatever they let me go to hell?
Don't let it bother you ... if you're not interested simply stop them and say "Thanks, but I'm not interested" and shut the door.
For the record I'm one of those dicks that is too lazy to share my faith and try to save your sorry butt
