As for why I go homeplug, there are a couple of reasons. I rent and move a lot and usually live in small places so even if the electrical is bad, there signal doesn't usually have to go very far, so I get pretty good bandwidth. Also, as a renter, I usually don't want to invest the time in dragging Cat 5 cable around a place if the cable will move with me, so homeplug is very convenient.
The last thing is that over the past couple of years the speeds for homeplug have gotten a lot better. Doesn't really matter when you have bad wiring, but the way my place is set up, it helps my router a bit if I can get a few things off of wifi and on to something wired.