When you need to produce a show with multiple who are NOT in your studio, Remote Production, the business chat apps do not work as well as you would like because they do not enable each remote person to com in to your production as a single, individual connection, with individual audio that a producer can manually mix (and fix).
Discrete inputs enables the producer to do custom designs on the screen for PIP, layouts, slides, and more. Things you just can’t do in Zoom, etc.
vMix is one of several tools available to facilitate more professional, better looking, better sounding productions with remote guests.