You know what, I believe you are 100% right. They are very narrative and they are very gamist.
I think that they are meant to frame a scene in a cinematic way to put the spotlight on the characters and make them shine. When setting a Skill Challenge, I think that the setting and objective must be very clear, what is at stakes. And what I like to do is to clearly expose each success and failure on the table for each player to see, it puts the pressure on them. Just like you show the clock to the players in a PbtA. For a Skill Challenge to work, everybody around the table must me on the same page, or it will feel forced.
It’s definetly not for everybody and I will never tell someone that he is wrong for not liking them. And I don’t think they would work well in a more simulasionist setting, it would feel weird… I don’t think I would ever run one in a 2e game for exemple. Good thing about Skill Challenge though is that I never thought they were necessary to run in a 4e game. It actually took a long while before I finally ran my first Skill Challenge. They are not necessary, just one more tool to put in my DM toolbox.