This is going to sound stupid, but... Don't you have to clean up for them to be able to come in and do their job?
Our major issue isn't so much that it's "dirty" per se. Granted that is an issue too, certainly. But the real issue is just that there are "things" everywhere. Kid stuff, papers or objects put down in haste, things that toddlers surreptitiously grabbed and moved into incorrect locations, etc.
All those things are why we don't get to truly cleaning. Wouldn't we have to get all those things picked up if we hired cleaners?