Well fitted quality leather doesn't "stretch" enough to a point of not holding the gun securely. Cheap holsters do. Cheap belts do too. I have Ernie Hill and Chapman holsters and belts from the 80s that still work perfectly. Good leather is expensive but it's worth it.
Leather is beautiful, but one characteristic of leather is that it stretches. I prefer a snug fit for my gun.
Kydex. Leather is for ass-less chaps.