Well, one of my concerns is that they clean the toilet and then may not clean their hands/gloves before wiping down or touching other surfaces. Another is wiping down surfaces with cleaning cloths that are dirty or have been used in multiple rooms. Do they clean the coffee maker the same way (with glass cleaner and a possibly dirty towel/gloves)? How about those nasty bedspreads (washed every few months, definitely not between guests) that some motels still have - I take those things off, fold them and put them in the corner when I arrive and Lysol the bedsheet that touched it underneath. I wouldn't want them putting those things back on my bed daily, either.
I just like to clean over that stuff when I get into the room and not worry about having to do it again on the trip (just the usual cleaning up after yourself thing). That first trip into the room and the initial once-over is typically the most stressful part of my hotel stay - I wouldn't want to repeat it every day if I let the maid in.