It's hard; once you have a car you've prepaid a certain percentage of your future journeys.
I think that's a major point, and one which makes me think some of today's younger generation have both a different attitude to money and a healthy resistance to Media propoganda and the UK concept of Class distinction. In my day (cliche), apart from a mortgage, you never went into debt. If you couldn't raise the cash, you did without - simples. Today, it seems money is a problem for the future, particularly ironic as our NHS crumbles, but hey.
As regards working it out logically - and I know circumstances vary in different parts of individual areas, never mind he country - public transport would seem to be FAR worse than it was a generation ago. I gave up the notion of driving in 1983, just four months after passing my test - absolutely appalling timing as it turned out, but a couple of specific events (irrelevant to this thread) led me to he decision.
When I did learn, I paid £7 an hour for lessons. 34 years later, I was surprised to walk down a street a few hundred metres from where I live and be passed by a L car advertising lessons for £11 an hour or £20 for two. That's barely 50% increase in over a generation. In the same time, single bus fares have gone up eleven fold and period tickets have also gone up well above inflation - particularly in the last two years. Petrol/diesel, at the pumps I believe has increased roughly in line with inflation for a number of decades, so with improved fuel efficiency, a smoothly driven smallish car costs less than 20p a mile to run. My nearest Supermarket is 1.5 miles away (0.3 mile walk to bus stop, and 1.2 miles bus journey. So if I had a car, it would cost 60p there and back, with room for plenty of shopping and up to extra passengers. By bus, it would be £4.50. The drive would be probably 15 minutes return with no waiting time. The walk/bus journey would be at least 20 minutes each way, and obviously the return would involve heavy bags.
Peak hour commutes would tend to have less stark a difference, but even if congestion increased fuel (and other variables) to 25p a mile, it would mean at least 6 miles each way before the bus matched the car cost wise*. A 6 mile journey at peak time would take maybe 30 minutes by car and 50 minutes by bus, even assuming you have direct bus.
Then there are the factors of unreliability/poor punctuality (although herabouts, reliability is good and punctuality is usually worse off-peak than at peak times); climate, waiting environment, overcrowding etc.
So, whilst accepting with some surprise that this is a positive development, I can't see it lasting in terms of people continuing to do without a car once they get into their 30s.
*Many - but by no means all - city centre workers pay parking costs. These are virtually non existant for shoppers and workers in smaller towns.