Not sure, but I know we shouldn't leave the decision of what is significant to a uncaring, money hungry corporation.

Future people, after seeing what is important to them. It must be available for them to save though.

If Hitler stayed in art school we probably wouldn't have cared much about him. But he didn't, so now we think his life or belongings and events are significant. But it might have been insignificant too.

Who knows? Time must play out.

Honestly, everything. IIRC archivists archive as much as possible because we can't know what will be significant ahead of time.