Peter I guess I can see what you're saying, and it kind of ties into what I've said in the start of the thread. Since a lot of non-free software/media has particular restrictions, it can be harder for people to redistribute and keep in supply. Not to mention, some corporate entities insist on "protecting their rights" even when they are not otherwise tending to their old stuff anymore. Meanwhile, FOSS and other stuff under free licenses can be redistributed without limit and the chances that various people have copies is higher. Hence, people might not be as concerned about that stuff getting lost. A lot of responses in this thread (and the original on the old forums) have indicated that there can be various nuances to this though, so that's why I ask around about it.
Checking in recently, the r/foss post unfortunately still hasn't really picked up any steam beyond one upvote from somebody (not counting the automatic upvote that appears upon posting.) As has been indicated, perhaps most people in the subreddit may simply not be interested in having this conversation. Searching around, I haven't exactly seen much discussion related to lost software/media (well, there is one post about a wiki that restores deleted Wikipedia articles, many of which are about FOSS, which is interesting but not necessarily the most related.) Of course, I'll still keep the post around in case anyone ever does take interest, whether sooner or later.
I'm still considering posting a version of this thread to the Lost Media Wiki forums at some point, and I'm also considering other venues to bring this conversation to. Suggestions might be helpful I suppose.