Like many households, they probably have a car already for other reasons.
To me this is big reason why transit has to be basically free to attract riders. It has to compete with marginal cost per kilometer of private car use, not total cost.
Marginal cost of driving is much higher than people think, because they don't count depreciation, maintenance, and insurance. There's a reason the IRS reimbursement rate is $0.70/mi.
True, though it depends quite a lot on the car. If you're driving a second-hand civic or prius, the marginal cost per mile will be much lower than a Mini or a truck. I don't know what it's like for EVs.
Where I live and with what I drive, once there is a single passenger, the car breaks even on the milage. But parking can shift things back in favor of public transit. It's close enough that traffic is always the deciding factor for which mode I take.
If transit were free, I would probably just take it most of the time.
This. No matter what is said to drivers in HN (and the "Real World"), they always have a good reason to drive instead of take transit. No worries about them. We, transit riders, can be productive (read, work, sleep, etc.) during our commutes.
To me this is big reason why transit has to be basically free to attract riders. It has to compete with marginal cost per kilometer of private car use, not total cost.