I don't disagree with you on the principle. But at this price tag (a significant part of the budget of a major Metropolitan area), you don't only need to know it's good : you need to know by how much it is better ; when the payoff is going to begin ;and how to you make sure you don't create issues which will persist for up to a century. Granted, large road projects aren't cheap either.

It also tie a significant amount of money each year to pay for continuous operation of these transportation, and for the moment, there is a significant number of transportation jobs which can't be filled. Roads are costly too, but can withstand these employment issue... for a time.

US cities probably should invest much more in this area, but there are limits to the ability of these project to solve transportation issues.