Gravity is very predictable: dust, crumbs and droplets fall downwards. If you start cleaning at floor level and then move up to surfaces or shelves, all the dust you knock off later will land on your freshly cleaned floor. You’ve doubled your work.
Cleaning from top to bottom – high shelves, counters, table tops, then chairs and finally the floor – means each step pushes remaining dirt downward towards the area you haven’t cleaned yet. At the end, you sweep or vacuum and mop once, catching everything that’s fallen.
It’s a small shift in order, but it makes the whole process more efficient and less frustrating. You finish with the floor, look around, and the room is genuinely done – not “clean except for that new dust patch in the corner.”