Even in Europe I was surprised about how they were punching through those expensive high speed lines. I understand that compared to short trip plane flights they save a huge amount of trouble, delivering you directly from city center to city center without the hassle of check in, security, taxi to the airport, etc. And since most European cities have good subway systems it's often easy to get from the train station to the destination.
Plus for city workers they make the 'effective commuting distance' much greater. Even in England (which is only semi highspeed AFAIK) people working in London are able to live quite a distance away now. Cheaper house values, no fighting with traffic, work on the train, etc.