“Didn’t the studios used to own movie theater chains...”
I seem to recall that in the early years, the owned the companies that produced film stock and cameras, as well. It’s safer that way. Otherwise, somebody might make an unapproved movie.
News report (1974) on Southwest Bell alerting customers that many are using illegally purchased store bought phones instead of renting (or buying) from the Bell company.
https://www.youtube.com/watch?v=cknKqJ9koyA