Why can't you wear a coat to this thing?
Because if there is a fire, people might die! Because of my coat!
Also, coats may be used to steal stuff from the dealerroom. My coat is magical like a bag of infinite holding and I can totally fit that random 1/8 statue of jailbait moe character #163 in there.
Or that they want to make sure female endowments are more visible?
You could be on to something... There are also very specific rules about where you should wear your badge. On the left side of your chest, which gives the gophers, stewards, staff and security an excuse to stare at your chest when checking badges.
Anyway, I'm pretty sure they have these rules for the sake of having lots of rules. They think it makes them look more important. I doubt they'll ever try to enforce rules like the coat rule, because that would mean they'd have to start a con-wide cosplayer hunt and kick out half of them.