That's not a surprise. People orient their lives around what they can do. Thus, things like this become self-fulfilling prophecies. You build it, they come, they add the demand, so you keep it running. It certainly does and has happened that cities have changed majorly at various times because of changes in transit, but it's not particularly common. In most cities even where transit has been torn out, you can see where the lines used to run because that's still a high demand corridor today.