That bothered me too. Trying a few though, it looks like they are 404s. Which is an interesting way to preserve a historical, but no longer valid link. If you are going to the trouble, it might be better to rewrite the links to point to Archive.org or something.
Linking an archived copy (and proactively making an archive submission when initially linking, which seems to be an increasingly common practice), would be preferable.
They clearly don't, despite 30+ years of whinging. (I've whinged plenty myself.) Preemptive defence is justified, necessary, and strongly advised.
The Web is not an archival platform, it's a publishing one. Each request is served in the moment it's requested, and absent specific measures for persistance can and will vanish at any time without notice.
