The Washington Post reports that it all comes back to a lack of money.
Ann Scott Tyson writes, "A quarter of Metro's fleet of about 1,300 rail cars have been in operation for more than three decades -- and another quarter more than 20 years old. Long stretches of track in the 106-mile system need repair, part of a massive $11 billion list of capital upgrades required over the next decade.
Yet even as the system has aged, the number of rail trips has grown from about 150 million taken per year in the 1990s to nearly 223 million last year, according to Metro data."
Thanks to Otis White