In the traditional model, you can only play one program at a time. One radio show or one movie or one show…
Scarcity of spectrum has changed just about every element of our culture. Scarcity of shelf space as well.
There are just a few radio stations in each market, and each station gets precisely one hour to broadcast each hour. Scarcity of spectrum, inflexible consumption (listen now or it’s gone forever).
There are only a hundred or so channels on most cable systems. Each viewer is precious and you can only program one show at a time. So program for the largest audience you can find, because that’s how you get paid. Share of viewership is everything.