because it has other people on it? personally I find that sitting down and getting passively carried near to my destination is way less stressful than paying attention to the road that whole time - not to mention finding parking. You don't end up exactly at your destination, but a little bit of walking is good for you.

Assuming you live in a locale with a reasonably efficient system. I've heard some horror stories about north american public transport. Other countries tend to do much better with timetables and routes.