Ever since the beginning...there have been cop shows, doctor shows, and of course, westerns.
War movies, not so much, and mostly concentrating on WWII, next to nothing on Korea and 'Nam
or our current Forever War. Until recently there was almost no science fiction, and as a kid I waited endlessly for horror and the supernatural, plentiful on the big screen but relatively scarce in pre-Twilight Zone TV.

Its all the market, of course, and all it takes is one lucky success to spawn a host of dreadful imitators. But surely there is some mechanism that manages to transfer the demand in the public subconscious onto the small and large screens.

And now, the smallest screens of all have a voice.

BTW, I watched "Rollerball" last night. From the '70s. Quite prophetic, bread and circuses, and the thirteenth century was lost altogether...