xkcd

I think square feet is popular because many things dealt with aren't squares, but a square foot is generally small enough to be a good measure, while also large enough to not be an unreasonably large number. When square feet are too small we move to yards (meters), acres, hectares or miles.

A house or apartment isn't usually square, so how would you apply feet (or meters) squared to it? While a property line might well be equally long on each edge, so you might see it in feet squared, but also that number looks A LOT smaller, so you'll often see square feet or meters