You have a waist.
You might be sexy, or have a nice rear, or killer obliques, or all the above, but wearing your dance pants like you wear your going-to-a-bar pants is going to make you look weird on the dance floor.
A) If you wear your well-fitted pants below your waist in the fashion of today, you will not be beefcake, but you will represent a different kind of pastry: muffin top. We don't hear much about the man muffin tops, but they are there, even for fit/skinny men who don't seem to have the ability to have any... overhang. Blame the skin-tight characteristic of dancesport clothing and the fact that a waist band has to bind somewhere to hold up your trousers. [Here is where I reeeeeeeeally want to post incriminating/helpful photos, but I won't.]
NOTE: Don't think you're safe because you're wearing one of those cool kimono shirts or because you're sporting an untucked shirt (which is a whole different problem) or because your shirt isn't tight (again, a different problem) because ...
B) If you wear your pants in the comfortable and less-old-man feeling "low rise" position, your well-fitted pants will not show off your terrific ass. SHAME. ON. YOU. I mean, a good 32% of the reason women do ballroom dance is to watch you fabulous men shake your fabulous rears. And we want ideal caboose-watching circumstances here, men.
C) Men, you've probably seen your dance partners. They're not wearing a lot, and they're not wearing things they wear on the usual, and they're probably not entirely comfortable in those things. (Except for maybe the rhinestone bra, OH WAIT, NO.) In a little move of solidarity, suck it up and wear your clothes in a way that makes you look hot, yet maybe not in the way that you'd wear them to your grandma's house. (Although, who knows, maybe Gramma loves a good open-chested shirt as well as me.)
D) And LENGTH! It's more important than width... Please make sure once you've hiked your pants up to what feels like Ed Grimley-like heights that your gorgeous ankles are covered. And your shoes. In other words, I want your pants touching the floor when you're not moving. And a stirrup around your shoe. Because I just don't want to see your ankles. And because the ballroom won't flood. Promise.