I don't mean materially private, I know we're fishbowls on wheels, but culturally private, as in people often refer to it as such.
It's one of the only times most people are disconnected from internet/work-tech because there is substantial risk of life and limb if they engaged (I know people have made this work regardless, I'm talking about cultures, not outliers)
Also this human need for privacy, if that's the reason to commute, is coming at the cost of literally destroying the planet.
There has to be a healthier way to satisfy these baseline psychological needs. Climate collapsing death machines may be how humans have transported themselves for a while but it shouldn't be the main go-to for how they are alone with their thoughts