Then you have never had to make up or return a hotel room to a "fresh" status. A few years ago, there was a TV show that was just about identical to "Undercover Boss." In it CEOs would do the tasks that their front line or entry level employees would do. One of the bosses was for a major hotel chain. He joined the ranks of the house keeping staff. Number one, he couldn't keep up with the pace that the regular employees moved to ready a room, and two, he could not believe how hard and how much work (physical and mental) that those employees did. It opened my eyes, too. It is thanks-less and low paying. If you saw the segment, you would think twice about not leaving a tip.
And why wouldn't you leave a tip (unless the room was dirty or not made up in time)? Do you tip at a restaurant, bar, taxi, delivery person? Why not the folks who make up your room? I don't trash the rooms, either. But when you need extra towels or you want something out of the ordinary it will make a difference. It's like the tire shop I mentioned. Do I have to tip? No. Do them remember the guy who brought the beer or flipped $20? You bet. I never want to be considered cheap (frugal maybe).