There doesn't seem to be even the pretense that we're getting music that uses multiple voices in harmony to convey some emotion or idea that can't be conveyed in the same way with one voice (or even one voice with background singers). I think the artist, producer, or label that figures out how to do that in this historical moment when there's an entire generation that venerates artists whose whole appeal is the absence of any musical ability whatsoever will be wildly wildly successful.From a marketing perspective the girl groups and boy bands of the nineties and aughts certainly functioned much more on the premise that they offered something for everyone—if you liked 'em blonde and sunny, dark and sensitive, or wholesome and generic, there was something for everyone. Groups, in a way, are geared towards the visual culture of our musical consumption. They're a full dance troupe, the cast of a video with multiple plotlines.
But they're also hard to keep together, as we've seen with the breakups of the Pussycat Dolls and Girls Aloud recently. In a group, rather than a proper band, not everybody has a definitive role that necessarily fits their skills and without which there would be a serious hole to fill. Nobody needs you, and if you can find a way to break out on your own, there's no compelling reason you need to stay. All of this is worse if your sound doesn't really gain anything from the multiple voices creating it. The incentives to find a way to go solo are significant if you're just a singer and dancer. Why be part of the crowd if you don't get anything out of it? The Supremes sound great, but it's not as rewarding to be Diana Ross's backup as it is to be Diana Ross.