Spend half an hour perusing that site and you'll truly see the pathetic state of preservation on the web. Outdated information, an endless list of failed projects... it's a self-referential call to action that documents our collective inaction.
A lot of the failed projects are not really due to inaction on behalf of archivers, but because the website being archived cut off the firehose too early, for example by adding a captcha. Most of the projects that have a page on that wiki have at the very least been added to the Warrior at some point and yielded a significant amount of data that was later uploaded to Internet Archive.
If you preserve "everything," you're sort of asking for a lot of those things to be outdated or no longer relevant. That's sort of the problem and why companies tend not to do so.
https://wiki.archiveteam.org/