> most of the people technical enough to set this up are also going to be technical enough to pull new cables.

It's really not that simple when you realize that the average UK flat has 3+ sockets and the average house has 5+ sockets (speaking from my own experience). Some daisy chained and some direct.

Besides, a lot of people are renting and cannot touch their wire.

> a lot of people are renting and cannot touch their wire.

Nobody's going to complain about a backwards-compatible upgrade (you can put phone sockets back when you leave - nobody has to know there's cat 5/6 behind it).