I mean I couldn’t do that either, not for very long at least. I have the tendency to walk around aimlessly when doing something like that (same when I’m on the phone), which means I have to clean the floor after. So mostly I either brush my theeth in the shower or I sit down/lie down.
Damn, I just noticed that my theeth brushing habits are probably very weird, bit hey, at least that way I do it 2 - 3 times a day.