what is wrong with a vasectomy if a women can't take birth control?
You have a few kids, and get a vasectomy to shoot blanks. No surprise kids, and you and wifey can fuck raw 
If you already had your kids then it would be ok.
If you're rich or a pro athlete then you should freeze some sperm and get a vasectomy so that some gold digging woman can't get you for child support.