The "Fair Weather Fan" Phenomena

In sports the bandwagon effect is often seen with disdain, mainly by loyal fans. This bandwagon, composed of "fair weather fans" often grow exponentially when a team is generating success after extended periods of below average performance. Stadium attendance and merchandise revenue grow to a point where one starts to question where this fan base was before. Despite popular thought (from "loyal fan bases") this phenomena is exhibited by every sports franchise in existence. My question is why is this seen as a social pariah.

On a consumer level these fans simply value another good (i.e all other goods on a simple PPF diagram) over watching a mediocre team. Preferences differ from fan to fan, so the main difference between a "loyal fan" and a "bandwagon" is simply how much they value their team. All of this may seem too obvious to most but how can fans look down on someone who may have a higher opportunity cost for time then they do. We exhibit this very same behavior in every facet of our lives and see it in the world around us (e.g the stock market, the food we eat, time spent reading over watching t.v., etc.) and are not nearly as appalled as we would be when applied to sports.