MRL Roller Lifter Street Durability

So my question is, if zinc is not important to a roller tappet engine why would we offer it?
I never said that but from my years in the dealership I can think of one other good reason when used in a
Harley Davidson Motor.

The air-cooled Harley Davidson street motor is one of the hottest running, most oil destroying powerplants
ever offered to the general public. anything that adds to the durability factor is a plus there.

Not to stray so far off-topic but you have to admit, that's a pretty valid point. I used to see HD owners filling
up with straight 70 weight Shell Rotella or John Deere oil made for diesel engines.