Some do train legs, some don't. 
It's a physique competition that allows you to cover your legs ~ 
It is what it is. 
Me personally? I would train everything, but for this particular competition's criteria, it isn't really necessary. 
At the same time, most of these guys are not bald and have to spend a lot of time on their hair, teeth and nails. Kinda gay? Depends on how you look at it. If you win a bunch of dough and get a good contract.... well ~