It's unusual, that's for sure. The interesting thing is that in some of those years, the 3 teams mentioned were one of the top teams in baseball in terms of wins, in other years, they were among the bottom of the playoff teams in terms of wins. So, it's not like they have lost so much because they were the weakest team in the playoffs every year.
Do those 3 teams have some kind of organizational philosophy that keeps them from winning in the postseason? I suppose it's possible, but if there is something, it hasn't been discovered yet. It's far more likely that it's just one of those fluky things.