Rooting for Losers:Why There Are Cubs Fans.

I would guess brain defect.
The Economist discusses the book "Scorecasting" (previously mentioned here), via the Dish:

It raises the question: does a team become a lovable loser simply because it loses? Is there something about losing that is inherently lovable? In a recent book called “Scorecasting”, Tobias Moskowitz and Jon Wertheim consider such “hidden influences” on how sports are played and won. In particular, they examine the effect of “loss aversion”—the tendency to care more about avoiding a loss than about making a similar-sized gain—on decision-making by players and officials. As The Economist explained earlier this year, Tiger Woods, for example, is more likely to hole a putt to save a par than to make a birdie.

Is something similar going on with spectators? To pick a team that is known to lose is technically to anticipate a loss, but in a manageable, predictable way. There is no real loss to avoid; a win would merely be an unexpected bonus. Backing a more successful team raises the stakes by making wins just as viable as losses, so losing is more of a loss.

Teams like the Cubs give people a safe space in which to lose. Fans get the benefits of commiseration without incurring any real costs. The predictable losers also allow other teams to win. So really the Sox fans should be grateful for the Cubs. Such losers may not be so lovable on scrutiny, but their ineptitude has an extra civic function: they take one for the team. They’re a sacrifice fly.

I can't resist posting at least once in a while about my hatred of Cubs fans and people who raise them.  Cubs fans are people to avoid.  The thing about rooting for a losing team was accidentally explained to me by an elderly Cleveland Indians fan in 1992, just before the club's mid '90's rejuvenation.  He was standing beside me just before the stadium gates opened, and he was explaining to a grandchild that the best thing about being an Indians fan was that you knew going to the game that the team was terrible and would probably lose.  You got to watch a game, and there was the potential that the team might surprise you and win.  So really, you couldn't be disappointed.  I think that sums up the above argument.  The Indians fans at that time were full of gallows humor.  It would be interesting to survey the fans to understand their feelings about the team's success in the late nineties, which in 1995 they came up just short of winning their first championship since 1948.   I would guess that overall, the fans think it was more fun being good, but not good enough, than it was being a laughingstock in the 1980's.  I would likewise guess that Cubs fans appreciated 2003, with it's letdown (I won't blame Bartman, if Alex Gonzales fields the double play ball, the Cubs are out of the inning) more than they have this season, lovable losers, or not.  I'd go with not lovable.