No, I think the disappearing crowd could be a factor. The fact that our mass transportation system is a colossal failure implies that this is not a major market.
People leave early from everywhere. They do it in St Louis. They do it in Chicago. They do it in LA. They leave earlier if their team has a big lead. They leave REALLY early when their team is getting destroyed.
They also leave concerts, parties, the movies and church early. The only place that people don't leave early is an airplane.
This notion of the DC fan base being somehow "lesser than" any other because they leave early is just silly.
If any manager makes his decision based on how late the fans stay, then we don't want them because they suck at baseball.