Most don't *need* it. But especially if you have time-of-use rates, swapping plugs isn't as convenient (or, rather, is more inconvenient) than you describe. It's just a nice-to-have, and in relation to the investment in the vehicles it's not expensive.
Ah, I forgot about those stupid TOU plans.
But even then, I can't imagine both people having to drive so much they need to charge everyday. But if you have to drive a lot, might as well be a Tesla.