Exactly. Monorail systems of the 1980s never really had their breakout moment, either, likely for a lot of the same reasons. Dedicated, elevated right of way can get expensive, not to mention the cost of each elevated station with ADA compliance. It also adds quite a bit of blight, which is apparent in the sample renderings.
I've been comparing the coming evolution of transportation to the evolution of computing. Shared servers (equates to buses), dedicated servers (equates to car ownership) and cloud computing (equates to the idea of on demand autonomous vehicle networks).
I think the sweet spot really is having these atomic units that can act independently (off rails, stop anywhere without stations) but are a cooperative part of a larger network. It's going to entirely change transportation. It's the first alternative I've seen for America that can genuinely rival car ownership.