In many cases, people ostensibly using stereo sound may as well be using mono sound. Stereo speakers built into a TV that's 20 feet away, or watching a video on their smartphone without headphones; technically these people are using stereo sound but with the speakers so close to each other relative to the listener, it might as well be mono.

I think if you want to make widely accessible audio content, you should be taking this into account. Make it intelligible in mono first, then worry about the rest.