I'm fortunate in that there is quite good public transport in my city, Edmonton Alberta Canada.
I live a mere 10 minute bus ride from work so I find it very convenient and Bus Passes run me ~$870 a year, which are also tax deductable.
Assuming a fully paid off car operating it would be $2-5,000 a year in insurance (depending on car/premiums etc.), add gas, regular maintenane, winter tires (its Canada afterall), and any potential repairs and the estimates don't seem unreasonable.
The real issue is that for many people public transit is not convenient or worth their time.
For me, 10 mins to work and I can basically get to anywhere I need to in the city in short order.
This has a lot to do with me carefully planning where I moved so everything is either within walking distance or one bus ride.
This only works because I am able to live in close proximity to almost everything I need.
Many other people simply do not have that that degree of flexibility.
If someone is in the situation where public transportation is significantly more time consuming than driving, or some other mode of transportation, I would completely understand why they would opt out.
I value my time highly and if my bus ride was longer than say 30 minutes each way and a drive was only 5-10 minutes, its possible I would be driving instead.