Five years ago (assuming you weren't exaggerating) the house builder chose not to bother calling Openreach about the new homes they were building. They chose to wait until the last minute and then say "We're a house builder, just put up a few new houses, so connect them to a phone line for us OK?"
If they instead engage at the outset, Openreach says OK, you need to put in ducting to run fibre to each house from the street and then along the street itself, our engineers will turn up and actually install fibre and enable simple phone service by default. But obviously when the engineers roll up to an estate with a dozen almost-finished houses "Dig up everything and start over" is not an option, so you get legacy copper phone lines. Too bad.
If they instead engage at the outset, Openreach says OK, you need to put in ducting to run fibre to each house from the street and then along the street itself, our engineers will turn up and actually install fibre and enable simple phone service by default. But obviously when the engineers roll up to an estate with a dozen almost-finished houses "Dig up everything and start over" is not an option, so you get legacy copper phone lines. Too bad.