I tip a minimum of 20 percent in food and drink situations.
I don't tip at all in hotels and timeshares unless I receive exceptional service.
Why the disparity? Because wait staff are specifically paid less in hourly wages under our laws with the assumption they will be tipped. There is no similar expectation with cleaning staff. The suggestions that one is somehow obligated to raise a cleaning staff's pay because they're not paid "enough" strikes me as quite odd. There are a lot of people in my life who I think should be paid more. Teachers, for example, are ridiculously underpaid, but we don't tip them.
I agree with you completely and would only want to add all of those that offer service to the not tipped list.