I think there may be license issues, if the archives are not in the public domains. Other than that, yes, they might as well sell them and "recover" some money.
Recordings that are not public domain are sold all the time... is there something that makes these different?
Just as with any other recording, I can make a backup copy for archiving purposes, but if I start selling those backup copies then that's a violation of copyright laws.
But this would be the copyright owner selling the recordings, just like a commercial album or movie.
In USA copyright, not in all jurisdictions. Backups and format shifting are not allowed in the UK.