I cannot believe the number of people who don't tip. If your company gives you a per diem or allows you to claim actual expenses, there is no reason that you shouldn't be tipping. Your per diem is supposed to cover housekeeping gratuities.
As another poster said, the people here on Flyertalk are well to do compared to housekeeping staff. You may not agree with tipping to subsidize wages, but that is how the service industry operates (at least here in the US). Your "protest" of this just sounds like greed to me.
Those who don't tip on pleasure travel are even more ridiculous. I have a friend who refuses to tip at restaurants. When I go to eat with him, I tell him -- if you can't afford to tip, don't eat at restaurants. What I'd like to say to Flyertalk is -- if you can't afford to tip, don't stay at hotels.
I am in an entry level position in my field. I make a decent living, but I am not wealthy by any stretch of the imagination. I always tip housekeeping. I spend 3 nights a week in hotels, almost every week. I receive a per diem which is supposed to cover housekeeping gratuities, and therefore, I tip housekeeping.