Actually it's mostly because everyone has given up trying to get about by any other means.
So far this winter on Scotrail, we've had the usual regular weather related disruptions on my local line to Glasgow. This happens every time we get strong winds as the sea gets blown over the electrified lines. Chaos at the weekend caused by staff shortages. This morning some of our staff at work were late (again) after 2 people were electrocuted on the line overnight, causing closure of the line. Unlike London, if our one line is closed, it's not possible to take a slight diversion.
As always, horses for courses. If I lived in London, I wouldn't want the stress of car ownership, unless of course I had my own private garage for the Bentley in the basement of my Mayfair penthouse. Living in any rural area of Britain, I wouldn't want to be reliant on public transport.