Well, my 102 grandmother apparently would be happy to jump on a taxi and return to her (rather cold and uncomfortable) house, instead of staying with my parents.
If she can figure it out, so most non-drivers. 
Yes, using a taxi can be expensive for longer distances, but factoring in for the costs of running a car (tax, service, petrol, cleaning, parking, depreciation, etc), it can be a lot cheaper per year.
Owl, I know what you mean. Ex once forgot his driving licence when we went on holiday. We had rented a car and had gone quite far away from the airport. I got food poisoning half way through and my dad ended up driving us to the airport, about 300 miles away. He and my mum returned by train.
My mum is one of those who has a valid driving licence but hasn't driven for ages, at least 35 years. Apparently because she's not very good and my dad was a very annoying back seat driver. True that he is, but I managed to get past it when I started driving at 18. It can be annoying because my dad is getting older and she needs to be ferried around, when she could easily just grab the car and go wherever she wants. I wonder if it's about control, as this way she always needs to have company instead of going about herself.
A friend of mine is going the same way, although she does get around a lot in public transport and taxis.