Perhaos it’s laziness. For many, I would argue it’s (understandable IMO) ignorance. I frequently see Platinums in Manhattan restaurants (even before the 10x-15x dining SUB). I think “regular” people just assume it’s the best card given the reputation it has.

Intuitively, it is clear to me why someone would assume the Platinum is superior to the Gold in every respect.

Thats why the supermajority of Amex’s top line is discount revenue!