Oohh, I just thought of another one:
That it is common for entire rooms in USA houses to not have inbuilt lighting and must be lit via lamp.
I can think of two reasons for this, in addition to what iridaceae said.
One, it is cheaper to build houses or apartments without built-in lighting. Especially in large apartment complexes, the builders save money on paying people to run the wiring, the wiring itself and the light fixtures. For one house, it's not that much money; for a complex of 200 apartments, it's a lot.
Two, older houses. Mine was built in 1900 and originally had gas lighting. Usually, when older houses were electrified around here, the wiring was simply run through the old gas lines. Not in this house. With the plaster walls and ceilings, the two rooms that do now have overhead lighting only have it because the ceiling was lowered, to allow for running the wires.
It doesn't bother me much, because I prefer lamps.