Sometimes we tip, sometimes we don't. It doesn't really depend on the cleanliness (we've never ran into a less than clean room, fortunately).. But based on if we have a greater than normal mess (like if the kids spilled chips all over the floor and then walked through it, ) or if we have a special request( like an extra pillow)
When we travel, I tend to leave a note on their notepad, thanking them, giving a tip of $5, and asking for extra pens (for souvemirs) . I get a "free" souvenir, they get $ for nothing OOP. We all win.