My garage at home and at work is perfectly level, so I do not use the parking brake. Any time I'm on any sort of incline when I'm out and about however I do use it. On level surfaces where there is no weight or force on the pin, I cannot fathom how that would cause any wear and tear or damage, especially since when I park at home the car doesn't even roll forward or back if I put the car in neutral. If you parked on steep hills day in and day out for many years and never used the parking brake or turned the wheels against the curb to keep it from rolling, I could see how that could eventually cause wear or failure, but I think that would be an extremely rare case. I'm sure the engineers realize most people don't use the parking brake and take that into consideration when designing a gearbox.