Leather and Kydex holsters have contact points where the holster meets the firearm. Depending on how frequently you draw your gun, those contact points will cause friction and eventually wear away the finish. If you draw your firearm on a daily basis, the friction created by the handgun rubbing against the holster while drawing or holstering will eventually wear away the polish or finish on your gun.
Select a leather holster lined with very soft and smooth leather, which reduces and/or eliminates the risk of abrasive friction.