I think you will find most OCers are quite fond of retention holsters as a matter of safety. So far as I know, all of these are either plastic or nylon.
Of course, I'm sure it would possible to figure out a good retention system for a leather holster. But I think that would be the key to getting any kind of widespread support for leather OC holster.
Now, I've seen a lot of VERY nice leather holsters for CC. But in those cases "very nice" means perfectly shaped, holding the gun well, being comfortable, etc, rather than having any ornate finishing work on them as they are, by definition, concealed.
Best of luck.