However, Backstreet Boys or many of the Korean idol groups do music that could be classified as choral that's highly accessible.
The main difference is drums. Music without drums or some rhythmic equivalent is less accessible.
The other main difference is not in accessibility, but economics. Is cheaper and easier to make a band with only one featured vocalist, so most professional bands do this. It's what people hear, and therefore what they identify with and therefore what they go out of their way to listen to.