When I am carrying something big and heavy down a flight of stairs, I need to be able to watch my feet carefully. This means that I am not able to carry anything large enough to prevent my being able to look down and instantly be reassured by the sight of my stair-descending feet.
I have tiny weak arms like a T-Rex, and small useless hands, so that even the lightest, most easily gripped furniture slips easily from my clutches. Also, I stop to shift my grip a lot, but I don’t tell YOU that I’m stopping, so you either fall over backwards or slam into the furniture we’re trying to carry. Then I yell at you.