California's high-speed rail has nothing to go for it except the typical alliances of baptists and bootleggers that pretty much define large-scale infrastructure project boosterism in the U.S. So it will go forward.
Large-capacity point-to-point modes (air or land) face a last-mile problem. How to funnel the crowds to and from each point to and from many origins and destinations? As cities spread out (as they always have and always will), the problem becomes more serious. Where the numbers of passengers involved is large, there are various remedies, including the growing array of private on-demand cab services. Markets and tech are formidable,
Where the numbers are much smaller, as they will be with rail, there are only the default public (also baptists and bootleggers) conveyances. Just as the post office survives long after it has been outclassed by modern alternatives, these will be maintained via the usual political patronage. Here is an update of the post office story. Think about it: why do we still have an old-time postal service?
The spreading out of cities means that there are origins and destinations near and far. This is why the sprawl story is so wrong. This is also why average travel times and distances are so stable (see Alex Anas, 2014)
Even networking and agglomeration occur over a range of distances. We all converse and interact with interested parties near and far. We share ideas (and research) electronically and we also get on airplanes to attend meetings here, there and almost everywhere.