What? 21 separate channels with different programming on each? That is a lot. The US has PBS for tv with many stations throughout the country, 350 of them. For the most part they show the same content. Then there is NPR with over a 1000 stations for radio.
They don't share the same content. I know because I have access to something like three PBS channels, 23 Public access channels, and three C-Span channels, and they show, random example at ~noon:
PBS channel
1) A pet show;
2) the same pet show;
3) a cooking show;
Public Access Channel (that's the name of the channel)
1) A B&W burlesque show (WTF? It shows that? Who knew?);
Public Access Channel 2: A program from some high school;
3) An orchestral doing music stuff;
4) A slide show from my local library;
5) a different orchestral performing;
6) An unmoving image of hell . . . wait, no, a page that just says "This channel is reserved for Public, Educational or Governmental Access programming";
7) A stick figure ... with the words "Let's act it out!" . . . and nothing else? Oh wait, the stick figure now has a crayon and a basketball;
8) An opera from, hmm, 1950? In Italian with English subtitles;
9) A broadcast from some classroom. Subject: umm . . gardening, I think.
10) No idea, a woman is talking directly into the camera speaking Korean (these types of Public Access channels do not show a title for a program, instead they just all say, for 24 hours/7 days a week "Public, Educational, Government Access", so you never know what you might find).
11) Public access channel that says "unavailable";
12) A list of emails and terms for the Dumfries city council (no idea why, I do not live in Dumfries);
good grief and 11 more Public Educational Government access channels. Probably more since they intermix these channels throughout my cable. those 11 counted below, not checked.
13
14
15
16
17
18
19
20
21
22
23
C-SPAN
1) Climate Justice Movement show
2) Brad Smith (President/Vice Chair) from Microsoft talking to a Congressional committee about Cybersecurity Failures at Microsoft
3) Lecture by David Eisenhower, grandson of President Dwight Eisenhower, about D-Day