The other reason around here easylikeasundaymorn is that all the traditional "starter homes" and maybe the next step (so 2 bed semis, 2-3 bed small detached houses) were on quite big plots with nice gardens.
The local executive 4/5-bed new builds are on smaller plots, so rather than move out of starter homes, people have extended them and stayed there.
It's almost impossible to buy around here unless you're a couple.