I've known since Marriott introduced their new bedding package that this little "backdoor" policy change was coming.
From Marriott's point of view, they committed to improving the look and feel, and perceived cleanliness, of their beds chain-wide.
Except that means washing duvet covers, which have not been laundered before, at every checkout. (You were lucky in the past if your bedspread was dry cleaned every quarter.)
Every Marriott has the exact same number of washers and dryers at their properties as they had before the new bedding rollout. But now, they're adding 33-50% more items to the laundry every day. It didn't take long for them to realize that their laundry costs would skyrocket if they didn't do something.
So, they quietly moved brand-wide to a standard of changing sheets every three days, unless the guest says otherwise.
Logistically, it was about all they could do, short of purchasing hundreds or thousands of new washers and dryers - and passing that cost to guests. (Or, perhaps adding an overnight shift of laundry workers in an already labor-short market, paying them a premium to work in off-hours, and passing that cost to guests.)
It'll be interesting to see if the backlash is major or minor. One thing working in their favor: Daily sheet change seems to be perceived by baby boomers and older guests as almost a right; but by Gen X and Gen Y, who have been brought up on eco-themes, as a waste of natural resources and a source of water pollution. As the population ages, it appears that daily sheet change becomes less and less a critical item to the overall population.