Cleanliness is a part of good hygiene. Rationalizing bad behavior is a tricky game. Sometimes it's as simple as the child doesn't want to do it because delayed gratification is a discipline humans have to learn because it's not innate. While underlying factors might exist for not doing something, we still need a word for that action. Laziness does in fact exist, but the argument that you're making is that it's not always bad. Fair enough.