With relatively little between the Bay Area and LA to serve as a viable customer base. Hence, a lot of the problems getting California HSR going. Imagine you had the Boston area and the Washington DC area and took out NYC and Philadelphia in the middle. You'd have the same issue. The Acela isn't the fastest rail service (in part because NYC is in the middle but Boston to NYC and NYC to DC are a lot more practical than the whole route. I did it once when I wasn't in a hurry but it was because I could afford the time.