Trapshooters know that a "round" is 25 targets. Skeeties on the other hand feel thay are endowded to shoot as may targets as they can during a round. No need to count, just take as many shells to the line as you TuTu can carry. Jake
The first day that I ever went to a gun club, a man asked me if I was going to shoot trap or skeet? I said I didn't know? He said if you want to shoot with the average man, shoot trap. He also said there are numerous shooters that shoot trap, and if you don't like someone, you can always blend in and not being around certain individuals.
With skeet, he said they usually pull up to shoot in their Cadillacs, and wear silk underwear. If you don't like a fellow skeet shooter, your stuck being around them as there is not as many as trapshooters. (True story).
Now here is what I feel is the answer to your original question. Back in the 70's Dan Bonillas was probably the first well known shooter to use just a holder from his belt with a box of shells in it.
Dan was probably more popular back then then even Leo is today. With that being said, shooters wanted to look the part and be like Dan.
Skeet shooters on the other hand had other role models to follow. They also usually carry more shells on them than trapshooters when they shoot.
Just my opinion.
Most of the trap shooters that I know are just good ol boys and don't like extra adornments of any kind. Whereas some of the sporties and skeeties seem to like to put on airs and have a "show the wealth" sort of attitude. And I think you have to be gay, not sure. JMHO Bill