It scares them, because one stray sperm can change a woman's life forever. But it can also change a man's. Once he's done with his pleasure, he loses power over its outcome. It's a woman's call next. And some women don't worry about the trouble that pregnancy might bring to the potent man who sparked it.
Stupidity is common in the heat of the moment.
That's why intelligence is required at cooler times. In the United States, vasectomies are the choice of only 10 percent of people who use contraception. At least twice that many use tubal ligation, especially Hispanic and African-American women. Men who choose vasectomies are overwhelmingly white and affluent. Most are in solid relationships and decide it's time to do their part.