It honestly makes sense to me... take a look at what Noctis can do, the fact that he can switch his weapons and warp, none of the other characters can do this. This alone makes for controlling the other characters just unappealing.
Looking past that though, playing Prompto would be third person shooter the entire time, which doesn't appeal to me that much. As for the other characters, just melee without the ability to do the cool stuff Noctis does.
Do I understand why people are a little upset with this? Yes, but I don't really agree, as I don't see the need to control the other characters. Honestly, there is no tactical reason to switch who you are controlling. Playing as Noctis will give you the edge in ANY situation, and playing as any other character for the sake of playing them is merely a gimmick to please players that want to control them. However, considering how limited these characters are, it would feel rather pointless.
Switching between characters was never something I was excited for, I was more excited for the battle system, the story, the environments, etc. Everyone is of course entitled to their opinion, however, I believe that I can shed some light on why this really isn't a big of a deal as some people are making it out to be. Being able to control multiple characters to give a weak impression of what "Final Fantasy" is supposed to be like just sounds like a joke to me.