My overly simplistic theory on why everything turns into a race-to-the-bottom is that cost is easily measurable and all the other things that Hart mentions, while important, are not easy to measure.
Some can be easily measured but would require significantly more regulation/data gathering; for example, calculating on time arrival and how optimal the route chosen was. Others would require publicizing data that some stakeholders might be resistant to reveal, such as the number of vehicle safety infractions they've accumulated in the past 90 days.
I think most people really believe they are all the same (and they might be right) and aren't willing to pay for a hypothetical benefit.