Meh, to each and all their own.
Personally, I don't see the appeal of leather--I think it's ugly. I much prefer the look of nylon. I imagine there are just as many people who think that metal chains are more attractive.
My grandparents used a metal leash to walk their rottie mix when she was younger. She was a crazy leash biter, and walking on the metal leash prevented that. Once she was a better walker, they could go to a normal nylon leash.