But but... they're unmentionable!

Personally, I've never been too fond of men's underwear. Boxers have way too much open space and are tight around my thighs, briefs are too thick which doesn't allow the material to "breathe" causing chafing and "swamp crotch", and boxer briefs are the worst possible combination of both! I'd rather go "comando" than wear men's underwear.
On the other hand, I
am fond of both the regular and low rise bikini styles. The material is thinner which allows for the material to breathe, thereby solving the problems previously mentioned, including the thigh constriction due to not extending beyond the crotch area. As previously stated, it's about comfort.
edit: I forgot to mention, they are also great for those who are not out yet and still present as male since the low rise, as the name suggests, do not rise above the pants waist line.