I can think of two possibilities. One is that the city authorities have come to think of the bikes as litter and would prefer to just keep them locked up in one area rather than pollute the streets again. The other possibility is that the bikes are in service, but the companies managing the bikes have no incentive to distribute them around the city again, and the potential riders don’t bother getting them out of the (possibly remote) corral. After all, according to the article, there are still a lot of bikes out there.
