@allison >but not everyone has the luxury of drilling holes for ethernet cables so they can be used across floors
For crappily constructed buildings with no clear internal wall path between floors, you just drill a hole next to the windows and run the cat6 outside (through UV resistant plastic pipe, as that's cheaper than UV resistant cabling).

If there is a clear path, you do based illegal electrical work (that is not in fact electrical work if you don't interfere with electrical wiring) by running the wires and installing wall plates.

There is also the option of powerline, which can be used with wired NIC's, too bad it's only slightly less bad than Wi-Fi and is asymmetrical.