Well, for me, it's just not feasible for me to take the gambles archive.org and others do. I am a professional locksmith in IRL, and "piracy" could lead me to losing my livelihood as my license could be revoked. I also have only so many hours in a day to keep stuff running. You think I need more mailboxes to be checked etc?
Plus, nowadays, dmca rightsholders will bypass you, going straight to the host provider who will lock you down for gods know how long until someone gets back to you.
I am not like Peter Plank, who ran nekochan.net. I have professional infrastructure,paid developers and a few sysadmins who help me run it all. It costs me nearly a grand a year to keep the lights on.
Is it worth the risk? Honestly, it's not! The only things I host are IRIX install media, and HPE moreorless said informally/noncommittally, "don't sell it and we're not gonna care!"
Thank you. Yeah, I could see why collaboration with archive.org would be extra work.
And also that you don't want any legal headache splashing back, such as if they get into a big copyright dispute (which, unfortunately, they have, in recent history).
