Earlier quoted context omitted.
Yeah, keeping physical things around does only make sense if it is actually valuable to someone. Archives only accept objects actually worthwhile of keeping. But it's different for digital content, as it's so much easier to store. At least for now. Also, Archaeologists love the garbage dumps and cesspits of old towns, literally the places where people put their least valuable things, because they weren't raided by ea…
Another way to look at this is that the more you store, the more difficult it is for people to actually find the valuable parts of what you've stored. One of the fascinating aspects of the internet is that our internet lives diverge so thoroughly from our offline lives - so the data we're leaving for the future is arguably horribly unrepresentative.
That's why you need to catalog stuff.
And if you have stored something, you can always get rid of it if you deem it to be unimportant, but if you haven't stored it, most times you can't get it back. Erring on the side of storing unimportant things is an important strategy to cope with that.