Sometimes stations do keep a record of their old broadcasts. But that depends on their size, organizational structure, funding, etc. some stuff is just lost to time simply because someone felt it was cheaper to just reuse tapes.
As for value, that's hard to determine. Depends on what was taped, when, by whom and in what kind of context. That's where curation comes in to play.
If you want copies of old TV shows that had bad DVD/BD copies, and can get through the VCR snow, then maybe... uploading that stuff anywhere would probably still incur the wrath of DMCA takedowns though, so personal use only.
Back in the early 00s, I had a DVR and for the life of me, I couldn't get a clean copy of some shows. Stations would always throw junk on the screen, and some repeats of repeats would also have them (and sometimes weird cropping angles to boot)
Of course, absence of that doesn't mean there's no value to anyone.