I'd imagine it's mostly subconscious bias. We haven't been good for a long time and it's easier to make the call for the team who "should" win.
Bad teams are usually up against it when it comes to officiating and have to be disproportionately competitive to their win/loss column before the refs start calling it properly, because by that point, they're now one of the teams that "should" win.
Bad teams are usually up against it when it comes to officiating and have to be disproportionately competitive to their win/loss column before the refs start calling it properly, because by that point, they're now one of the teams that "should" win.