First, let me add to Mare's point. It's not only that they're not serving you the food. It's also they're not taking the order and making sure it's prepared according to the order. Not getting your bill and you out on time.
I think the 10% is too small. I'm with N'cat (surprise). At breakfast, I'll do $1 per beverage served, like a cocktail waitress. This means I usually leave $3. At dinner I'll do a little more.
I don't get why people will hand dollars after dollar over to a cocktail waitress who brings 4 ounces of beer or cola and short the housekeeping staff (who are in your room with all your stuff!) and the buffet waitstaff.
What wasn't raised is tipping the line crew (cooks). I don't like people putting dollars our for omelets or carved ham or whatever. There is no tradition to tip cooks.