I take a different view of the service industry.
I'll leave a buck or two for that guy/gal who tidies up the table, removes my plate or otherwise does something helpful/useful. Yeah it's their job, and that's what they're suppossed to do. But I've got working class roots which acknowledge effort, especially when it involves service folks who depend upon customer good will. Especially so given these tough times we all live in. That's just my own view of the world.
As to the tip jar. Sounds a bit tacky in any Marriott situation. I've not encountered this yet. Still, I suspect that it flows from the sour economy.
Barry