On public transit, on the other hand, I can relax and read and pretty safely ignore the world. Worst case someone grabs my kindle or my phone and runs. I can afford a new phone. (which hasn't happened to me; I'm just saying, that's the biggest risk I see on public transit from relaxing my vigilance. In a car, well, a lot of people have killed other humans because they let their attention wander or decided to change the radio station at an unlucky moment.)
I mean, I'm not saying that your view of comfort is invalid... I'm just saying it's not universal.