Many people don't listen because their stuff works good enough on wireless. If wiring is already in place, or trivial to set up (e.g. because the PC is next to the router) they'll do it, but I can understand that they don't care about the effort if they don't see a benefit. In my experience, people that actually have issues with their WiFi are easily sold on cabling, as are those that really want performance. If stuff doesn't work, tolerance to spending money or ugly cables laying around goes up a lot.