Because there’s nothing better than Keith and Shiro being a duo… a pining duo. For years. Until Keith finally confesses to Shiro on stage with a song - without Shiro knowing what’s going on at first of course.
Allura might be their label manager or something. And Pidge and Hunk are the tech support (because I think neither of them would enjoy standing in the spotlight. They’re more like the people making sure everything’s working backstage).