Why would anyone get a vasectomy?

Maybe because the man is in a committed relationship, his significant other and himself have kids together, and don't want more. Maybe they feel like the woman shouldn't have to be on birth control the rest of her life just to prevent them from have another child (because that's extremely unhealthy) so the man steps up to the plate and decides to get a vasectomy. And don't tell me "just don't have " because honestly, that's not gonna happen! That's how you end up with the "oops how did that happen" baby LOL.