Because some people are player fans, not team fans. The downside of having a generational talent like Wemby is that we just attract a lot of these fans. Some even flat out expressed, multiple times, that the team is making Wemby look bad as if that is something we should be worried about. The Spurs losing to the Suns by 12 points wasn't the issue, Wemby looking bad because he only scored 9 points was, as that will impact his MVP chances and future legacy. It's almost laughably as a) I am a Spurs fan and I am not overly concerned about Wemby having a bad game here and there, as long as he improves over time (which I definitely thinks he will as he clearly has the mentality for it), and b) MVPs and all time greats have bad games.
It reminds me of those Kobestans, don't give a crap about the team, they would ignore the fact that Kobe essentially destroyed the Lakers since 2014, for a solid 6 or 7 years, but as long as Kobe got his, it's all cool.