For anyone curious, you can help fix dead reference links on Wikipedia in just a few seconds. If you find a page that has a dead link (or several), click the "View History" tab at the top, then click "Fix Dead Links" to run the InternetArchiveBot on the page.
Genuine question. Why isn't this done automatically? Astronomical (even suspicious) amounts of continuous outgoing bandwidth?
Just speculating but possibly the difficulty of finding a truly dead link. Often they just redirect to a registry asking if you want to buy the domain.
but redirects are also present in legitimate pages
Wikipedia is working with the Internet Archive to automate the prevention of link rot.