Their goal is not to reward us FTers with additional discounts for things we were already doing but rather to try to drive incremental spend from others who might not otherwise have done it. So it actually does make sense they would tend not to reward people on an affiliated card, since holders of those cards are presumably already pretty engaged with the brand.

That being said, I just noticed one on my Bonvoy AMEX for "Get 20% back as a statement credit by using your enrolled eligible Business Card to make purchases on room rate & room charges at participating Marriott Bonvoy® properties in the US & US territories, Canada, Mexico & the Caribbean from 1/12/2024 to 3/31/2024." I'm sure it hasn't been there since 1/12, or maybe I had too many other offers clogging up the slots or something (I forget if there's still a max of 100)

EDIT: I just noticed the T&C say business card, but this is a personal card. It let me add the offer anyway -- will see what happens, I have a stay coming up in a couple weeks.

I've definitely had them in the past as well, and DL offers on my DL card, etc. but it does admittedly seem less common, subjectively anyway.