> I've never understood the pseudo-ephemerality of instagram. Even if you save stuff, or like it, the interface makes it very difficult to recall stuff from more than a few days ago.

Hypothesis: these businesses all monetize # of interactions (even if CPI is low), which they want to maximize by structuring interactions such that there is constantly new content that encourages obsessive checking. A sense of ephemerality of content reinforces that behavior ("I have to check because there is new content and it may be gone if I wait to check").