Good, working and efficient public transit still means having significantly less comfort compared to having your private vehicle. Pretty much the only exception is using the metro in a congested downtown area at peak traffic (still, your metro experience will also be degraded by the peak traffic), or perhaps if parking your vehicle will be very difficult. And i say this as someone in a rather big city in Europe who is currently only using public transit. And there is a lot of stuff that i'd like to do but i can't do since i currently don't have access to a car or motorbike.

People don't just want "useful", at least the majority of people in developed countries also want "comfortable", and "nice", and "easy", and "enjoyable". A peak-hour metro ride or missing your tram by one minute is none of that.