It's funny because in practice probably all of us use Wikipedia as essentially gospel when it comes to almanac facts such as historical people's birthdates or survey numbers, ie average rainfall or the region some tree owl lives in.

Precisely because we expect that Wikipedia has sourced this information, such as climate data, from a reliable location - i.e. not made it up for itself.

The great thing about Wikipedia is that you can very easily see if something is sourced and where it is sourced from.

Trust, but verify.

well, checking the source can be complicated, if it's a web page that had disappeared before being archived or a book/publication.

The link rot on wikipedia is pretty bad.

I don't really have an easy solution. People aren't doing it in bad faith. Do laws prevent archiving for the purpose of referencing? IANAL but it certainly sounds like one of the copyright exemptions.

If so there could be a "wikisource" that fetches sites when referenced and then archives them. This isn't IA, it's a different goal really.