I don't understand why it has to be such a battle every time. For almost all of my 1000+ Marriott nights, I checked out before 8:00am. Marriott benefits from that.

In the few instances (usually on vacation) where I could use some of those hours back, it typically goes like the following:

Me: I'd like to request a late checkout. I arrived at 11pm on my first night.
Hotel: I'm sorry sir, but we are completely sold out/fully committed.
Me: I'm a Marriott Platinum Premier. Doesn't that offer late check out?
Hotel: Oh, I see that. Let me check. I can do 1pm.
Me: My flight doesn't leave until 4pm. Is there any way you can do 2pm?
Hotel: The best we can do is 1:30pm.

For the number of nights I stay, SPG offers the ability to customize my 24-hour period. On my vacation travel, I typically arrive very late at night and want to depart 2-3 hours late. That's where Marriott doesn't typically meet my needs, although I do get an occasional exception.