Shouldn't be a hard sell for OEMs; official specs are 64 GB is enough storage for windows 11, and I can get a 128 GB SSD for $15 retail, whereas the lowest price hard drive I can find is $25 retail (500 GB, but 3.5"), so if you're a cheap PC OEM, putting in a crappy, tiny, SSD saves money. And the only systems without SSDs I saw on BestBuy were refurbished machines shipping with Windows 10.
Marketing won't let them so long as it would piss off PC OEMs that still ship crappy systems and want to use the Windows logo.