The band is always playing in front of you, even when you're in the front row at a stadium concert. I don't know why I'd want to hear the bass guitar coming from the side speaker. Maybe for karaoke...
I mean, this is a matter of taste. But there's no reason to limit yourself to physical or historical limitations that have nothing to do with the actual medium. The technique isn't new or anything either, Pink Floyd was doing it 50 years ago. Artists can and should put whatever they want in whatever channels they want.