Taxis exist.
A quick search suggests that here in the UK the average driver is spending up to £200 per month on their car (excluding any financing to pay for it in the first place). That much money would easily cover a monthly travel pass in most cities I’ve lived in, with plenty left over to pay for taxi rides when you need the convenience of door-to-door travel at a time that suits you.
I live in London zone 5, travelling to Zone 1 will cost me £267.30 monthly. One of my colleagues lives in Petersfield. His monthly ticket would be £613.70. You don’t know much about train fares in the UK, do you? If you live in Scotland and need to travel to London, it is always cheaper to bloody fly! Sometimes it’s cheaper to buy a car for one trip and then just dump it, or, even better, sell it and recoup your costs!