The window stickers still list both. Even filtering for gas, you'll find nearly all Rebels.
I think the build and price is just because customers don't care about the underlying architecture, they just want what they want. At least the options are mostly correct, unlike the Canadian site which sent me down a long fruitless search for OEM PW aux switches. Their site swears its an option, has for years...they don't exist.
I almost never see another PW where I live. The only place I saw them relatively often was Jackson Hole, but stupidly expensive trucks are like Camrys there. Raptors and PWs, especially. Only peasants drive a King Range in Jackson Hole...