It also says only 4 major channels. Nobody would have had access to all 12 at the same time.

Most places would have just the major with a few having an additional local channel, such as NYC, LA and Chicago.

TV broadcasting was expensive and required a tower. There had to be enough people to get advertisers to pay for programming. Towers could only send a signal so far. Even people in the same town might not get a channel if they lived on different sides or if the were on a hill or in a valley.

It was nothing like it is today.