There’s that, and also part that’s donations by viewers and sponsors. While they need funding to maintain operational costs I don’t think they have the typical pressure of expecting a return on investment to deal with, so volunteer supported archiving, hosting via things like peertube or youtube without needing to show ads, there’s room for some novel operations that other content producers don’t have.
I keep saying, if this stuff is publically owned works made by the corporation for public broadcasting, put up some official torrents and let the public archive it for free. Mr. Rogers would surely approve of sharing for the common good.
I expect there’s some kind of TOS rule about scraping and recording of streams. Making it opt-out allows Twitch to sell those streams to AI companies similar to how Reddit did after going public.
So by that token if someone digitizes a physical medium and makes it available to the public copyright is no longer valid. Otherwise, having it ingested by an AI has no purpose it it’s not meant to be referenced in response to requests by the end user.