Everything I do is for utility's sake.
If you're wearing pro-tan, you're going to make a mess on your clothes.
Also, if wearing plastic to drop water in the last 24 hours, you're going to sweat.
And, if you're jacked on ECA or clen, or worse, lasix or DNP, you're going to be sweating.
And if you're going to be taking off clothes for posing, weigh-ins, etc, a suit is going to be cumbersome.
And, you're going to be in unfamiliar backstage areas where hangers might be scarce.
And for that time between pre-judging and night show, you want to be as comfy as possible.
For most people, a sweatsuit makes more practical sense than a suit. Suits look great, but for most of the trotting around that comes with a show, a sweatsuit or jump suit seems more practical.