These two pictures explain everything better than words can.
Serious answer though: He's the only eligible bachelor left among the Z-fighters. They're already way stronger than everybody else on earth. Who else would she have gone for? Goku and Vegeta have families. Gohan is a kid (
) Future Trunks ends up going back to his own timeline. Piccolo is from a race of asexual aliens. Tien? He's awesome in a fight but he's BEEN on the downlow with Chaiotzu. Who else would she settle for?
Yajirobe?
Master Roshi?
Yamcha?
Krillin borderline simped her for sure, but he's definitely got more going for him as a husband/father than the rest of the available crew. He was the first one to realize that the Androids weren't all bad and the only one to treat them more like actual people.