For what reasons will a straight man get a vasectomy?

Birth control: Am i missing something here? Vasectomy is a surgical form of male birth control - it renders a man sterile. Sterile men can no longer father children, but they can be sexually active, have erections, etc.

Done w/ having kids: Vasectomy is safer, cheaper, and more effective than a woman getting her tubes blocked/tied. It will not affect a man's sex drive or ability to ejaculate b/c that's dependent on the prostate/seminal vesicles that aren't affected. It's irreversible; ppl who try have limited success. It takes 3 months to make sure the vasectomy worked and is not 100%, but very very close. No needles/scalpels needed!