If you own a house, you definitely have money for a wifi setup with multiple APs - like Ubiquiti with three APs and PoE switch and dedicated gateway - I'd love to play with that, but I'm not going to buy a house to do that.

And for people living in apartments, where every apartment has their own wifi network, less penetration is really a good thing, because there's less interference from other apartments.

This is assuming that intra-apt walls magically allow wifi penetration whereas inter-apt walls magically block it.

Neither of these things are the case, tragically.

If you have nice, solid walls, the signal will mostly bounce off them and pass through doors.

It will usually pass a single wall, so you will hear some first-degree neighbors, in some places, but it's significantly better than interference from 2nd degree neighbors.

Agreed