The most compelling reason for a Marriott Gold/Plat to stay at a hotel on a weekend is EEO. Of course, this is mainly U.S. hotels, with any property randomly designated as a "resort" off-limits. But it's still a lot of properties...and quite a few good ones.
Of course, this requires a 2-night stay. I'm only doing a 1-night stay this weekend. Therefore, I'm sending this post from Sheraton...
Also, this fall I've noticed that most Marriotts are offering breakfasts (up to 2 or sometimes 4 per room) plus a $100 Bonus Bucks for either free or a very trivial cost ($10/nt. or so). I have three of these stays coming up in the next few weeks.
But yes, I agree with the general point that it's a shortcoming of the program as a whole. The special "resort" rules bother me the most - withholding benefits on weekends seems to irritate many on a basic fairness level, but the flip side is that the EEO is a perk that nobody at HH or SPG regularly gets.