That's entirely the point. Lawns originated in the middle ages as a status symbol. They demonstrated a) that you could afford to waste a perfectly useful piece of arable land and b) you could afford to pay a team of men to neatly scythe and shear it. It's hard to tell how much land an aristocrat actually owns, but the size of their lawn acted as a reasonable proxy.

The invention of the mechanical lawnmower helped to democratize the lawn, establishing it as a symbol of middle-class suburbia. A small lawn in front of a suburban house didn't demonstrate that you were gratuitously wealthy, but did demonstrate that a) you could afford a larger plot of land than strictly necessary to accommodate your house and b) you had leisure time to spare.