The Archive Team only backs things up when there is a risk of them being gone.

They cannot do it any other way - the Internet Archive does not have infinite resources to host things, and they need to prioritize. 120TB is not an easy thing to host.

That's what the Internet Archive tries to do. But they have finite (or rather, extremely limited) resources. The Internet is vast things fall through the cracks.

The Archive Team is the "oh shit this site is shutting down and it's not all in the Internet Archive already, we gotta save it before the deadline when it's gone forever" squad.