Should they? Do you think other people honestly don't know how expensive driving is, and should consider going carless?
I'm not on about people deciding not to get second or third cars, by the way - though I note your other points (We have one car in the household too).
I think that there definitely people who don't understand their full costs of car ownership when they mostly focus on only fuel costs.
For example if you replace tyres every 15,000 miles at £75 per tyre or every 25,000 miles at £125 per tyre that's an extra 2p per mile.
Even little things can add up quickly, for example paying just 50p in parking for 1 day a week is an extra £26 a year.
Most people these days would be paying out around £5,000 for a car in depression, over 4 years that's £3.40 every day regardless of if the car is used or not (the average is £5,250 over 4 years and equates to £110 a month).
That means that if the car is going less than 22 miles on that day (that's the same as about 8,000 miles a year) that puts the same cost as the cost of the fuel (15p per mile).
Also there's a lot of costs which people just pay because they are small amounts each month, even if they rise significant at the annual level. For example if an insurance payment goes from £62 to £70 a month that's basically an extra £100 and that can easily rise from £62 to £78 per month over three or four years without people potentially being fully aware that their annual costs have risen by about £200 a year over that time.
Yes your should be reviewing things like insurance each year, but sometimes rises are unavoidable.
Then there's all sorts of other small value items (screen wash, car accessories, washing equipment, etc.) however some will pay a lot more than others, for example some may wash their own cars, but take it to a car wash and those costs increase significantly.
That's before you consider the value of your time to do things like take the car to get it fixed (or fix it yourself), washing & cleaning the car, and the time taken to do all the car admin (including finding and buying your new car and potentially selling the old one).