The lows are very different when you have money and when you don't have money.
When you are struggling financially and a single event (e.g. car breaking down) can spiral into wrecking your entire life, you it's hard to "let go" of that.
When you are financially stable there are a lot of frustrations (e.g. work stress) you can learn to cope with, control, or let go of.
If the same thing happened today I could just shrug it off and carry on regardless.
I am not rich now but I have spare cash and this makes an immeasurable positive difference in ways one cannot conceive without the benefit of an alternative experience.
* If you're broke and the car breaks down, it's both a car crisis and an extra financial crisis (need money to fix the car).
* If you have enough money saved and the car breaks down, it's merely a car crisis ... and, given that you're capable of fixing the car, it's less of a crisis, at that.
The whole dynamic changes.
For example, I live in Canada and unless you life in the capital of the province everything is really far away.
A lot of people live in cheap apartment blocks of rural areas and it can be a walk of pretty much an hour to get to the groceries store. There is public transit but it's usually every few hours instead of a constant traffic, so you have to plan your entire day around it.
I do agree with your main point that public transit should be one of the main investment of a country.
When I was unemployed for a while even the smallest problem was all-consuming because I had to worry about losing my last money and everything else.