Because competitive games are a cesspit. Even games with highly competitive PvE aspects have this problem (MMOs, most notably). Ironically, those are also the games which allow for the highest time investment for the common player. Mostly because everyone is online and anonymous, which subsequently keeps their filters from activating.

By comparison, I've never had a local game of Mario Party remotely as heated as the average experience in a competitive, online game. Not even after Chance Time did the unthinkable.

The downsides of Disney are a little more subtle, too.