And in a lot of cases, the actual citations or references used by Wikipedia are dead links, or have some sort of 'last retrieved at' annotation, or end up at parked/squatted domains and the original content is no longer there to validate the claims it supposedly made.
Offhand I don't know if Wikipedia has a policy on references to Internet Archive / wayback-machine links to things, but imo, being able to point to a snapshot of a reference at the time it was made, as well as the current version if it still exists, is a desirable feature, and well worth striving for.
Internet pagerot/linkrot has caused me grief with bookmarks for things I didn't realise I needed again until years later when they were gone.