I have three access points at my house: One on the second floor, one in the basement, and one in the garage. (The AP in the garage is a repeater, with a hacked router doing bridged client mode (not wasteful WDS) wired to another hacked router being a simple access point.)
I didn't always have to do this: Back before the neighbors all had Wifi and a million Wifi widgets all streaming Netflix and Youtube, I had reasonable coverage all over my house and yard with a single WRT54G with a parabolic beer can on one of its antennas.
But now I have to do this just to get a simple Pandora stream running reliably in the garage (20 feet from the house), much less the garden at the back of the lot.
I try to use it efficiently, with the radios only putting out enough power to do an effective job. I manage channels carefully, so that the most-used channel in the neighborhood is the one that is in the basement (where it radiates least), and the least-used channel is used in the garage (where it radiates most), to help mitigate co-channel interference. I always hard-wire my devices if they allow me to do so, to keep wireless spectrum available -- even though I rent (old houses can be ridiculously easy to non-permanently cable).
But when I can sit in my living room and see 17 access points that don't belong to me, with manufacturer-default SSIDs, I know I'm amidst hordes of folks who are using the spectrum for fixed devices: The streaming box by the TV, the old desktop in the kid's bedroom that does Youtube livestreams 8 hours a day -- that sort of thing.
And that's just inefficient use of the spectrum. Fixed devices should be wired if at all possible: Period.
If pre-terminated cat5 cables were cheaper (and I know that quality cables can be very cheap indeed, but they're pretty bloody expensive at Wal-Mart), I think I'd see a bit less of this problem. When it comes to buying a $20 wire to hook up the Fire TV to the 75Mbps modem, or buy a pizza to go with that streaming movie: It seems that most buy the pizza.
I can't say that I blame them. But I roll my own wires, or buy the $2 Chinese imports from deepsurplus.com which seem to be as good as anything else, so I get pizza -and- high-quality streaming -and- improve spectral efficiency of the neighborhood.