If you don't see an error in your premise being pointed out, then you need to put your "posts expire and get deleted, like on Usenet" right up against "people were not expiring non-binaries posts on Usenet" until the penny drops.

Then you need to notice the point, already made by others as well, that the premise of ISL's question is erroneous, too. The storage requirements are not necessarily "tremendous", if one actually learns from the past. Again, your comparison to Usenet needs to involve considering how Usenet treated binaries and non-binaries very differently. (One can look to experience of the WWW for this, too, and consider the relative weights in HTTP traffic of the "images" that ISL talks about and the non-binary contents of the WWW. But your comparison to Usenet does teach the same thing.)

Your and ISL's whole notion, that everything is going to get tremendously big and so everything will need to be expired, rather flies in the face of what we can see from history actually happened in systems like this, such as the one that you made your comparison to. Usenet did not expire and delete non-binaries posts.

By making this comparison and then trying to pretend that it's someone else's non-sequitur you are closing your eyes to the useful lessons to actually learn from your comparison. Usenet, and the Wayback Machine, and the early WWW spiders, and Stack Exchange, and Wikipedia with all of its talk pages, and Fidonet in its later years (when hard disc sizes became large enough), all teach that in fact one can get away with keeping all of the "non-binary" stuff indefinitely, or at least for time scales on the order of decades, because that is not where the majority of the storage and transmission costs is.

People have already danced this dance, several times, and making a distinction between the binary and the non-binary stuff and not fretting overmuch about the latter when one looks at the figures is generally where it ends up.