Because it just wastes wax paper, which, being waxy, attracts dirt and dust. A nice little breeding ground.

How hard is it to wipe the top of a fridge with a wet cloth and a couple shots of degreasing spray? I buy degreaser (Super Clean) by the gallon ($10), make my own diluted spray. That gallon lasts years, and works better than the expensive stuff.

Using wax or parchment for a tray that catches grease under something makes sense - then you just ball up the paper and pitch it, rather than waste gallons of hot water trying to clean the tray.

These kinds of people should work in a restaurant for a while, see what's involved in properly cleaning/maintaining a kitchen.