What is the problem with using only half a bucket of lukewarm water? Chapter 2, part 3

Using only a half bucket of lukewarm water means that you are cleaning the floor with dirty water. The floor isn't clean, the dirt has just been moved around.

We are instructed to use less than half a small bucket of lukewarm water for a kitchen and all adjacent scrubbable floors (breakfast nooks and other dining areas), meaning that within a few minutes we are doing nothing more than redistributing the dirt evenly around the floor.