Because I am fed up of trawling through pages and pages of identikit new boxes when I want something older and with a bit of character. You can ask for new-build or not new build, but so many new places are bought and then put back on the market straight away they might as well be new-build.
Local property market swamped with new houses due to monster estates being built in the last few years. The older places seem to be few and far between.