I spoke with a bt engineer on this very subject a few years ago and I was told that they can't at the moment. Reason being is emergency calls in case of power outage. As you know, you can plug a corded phone directly into the phone socket and its powered by the line alone. This would not be the case for fibre and would put people at risk in the case of power failure.
I do agree though, wtf this country does not have fttp fully rolled out at this point is a case of greed. They're rolling it as quickly as they whilst maintaining the best possible share holder payouts, same as the the other utilities. This is why it should never have been privatised, same as the leaks in the water system (over 3 billion litres a day leaked, hence the restrictions) and the gas, as we're exporting most of what comes out of the North Sea as there's no storage for it here in the UK, even though the volume we take out in the North Sea would cover 80% of the uks usage. Same with electricity, they could have built more solar farms, nuclear power plants and wind turbines but again, making sure the shareholders got a good payout was the priority. And wheres the taxes? In some tax haven. I hate the greedy world we're living in, I fully see some kind of elysium style future for us and it's vile