Which is fine. These people are digital hoarders, desperate to save threads of puns on pictures of cats. None of it matters. You're not going to go back and look at all the pictures and threads you've posted. Life goes on.
I disagree, there's tons of valuable content on Reddit that people regularly reference years later. Tech support, product reviews, and similar. You'll often see people on HN recommend searching with `site:reddit.com` based on the valuable information it holds and the degradation of search result quality.
Saving content from forums is the same idea. Reddit is just a collection of forums.
There's more than enough evidence of that in a billion different places. And we're not exactly suffering from not having those records of the past, either. If keeping records long term were actually important we'd have done it well before the sites end up deleting all their content. This is just a fear of the unknown with no concrete examples of cases to justify it.
I agree with the hoarding bit. I'm not an fan of that either.
But I'm much less of a fan of the self importance of tech pretending this "data" has any more use than temporary ad surveillance until they delete it or resell it.