Well, yes, if you're OK with it looking like crap sometimes. Not ALL yards are suitable for a walk behind. I have quite a few that I still cut with a 21" because the terrain leaves you with high and low spots and other issues that I'd just as soon avoid. If the lawn looks better cut with a 21", that's what I'll use. If by "every", you mean "huge lawns and tiny lawns, but NOT everything in between", then yeah, I agree. But that isn't reality. THAT is reality.