The majority of Marriotts are in the category 1-4 ranges, hence the 1-4 certs continue to have value. Not as wide a choice as they were 2 years ago, but then what was the cash rate 2 years ago?
As previous posters have pointed out, on megabonus these certs require little commitment to receive, 2 stays=1cert, compared to $1000+ spend required to earn 20,000 points. In my view these certs are of some use, though much less now than they were. The offer of these certs certainly won't drive my stay behaviour now, and with more customers taking that view, it could leave Marriotts megabonus stay/cert offering failing in its promotion objective.
Now the cert with the MR card... Well we don't get that here in the UK, but I'd certainly be questioning renewal when my fee becomes payable...