Alright but I'm not understanding why they would rather booked with points than free nights.
By booked did u mean upgrade?
Simple by using points u show loyalty to the brand because how else would u have gotten them (they don't think cc) if not by staying at hotels. Free nights they don't feel like you did anything or spent money by Marriott to deserve anything. And most suites are residence they have to "pay" to use them so why give the room to someone who never spends money on the brand.
Waj told.me the same thing they upgrade quicker to people who come on points then free nights.
I was told one of the rare times they upgraded a guy to the presidential suite was when a guy dropped over a million points on a 1br suite for a few days.