Let's be honest... we're sometimes lazy or forgetful so even if we see the value in archiving (not just for the preservation value) it often doesn't get done.
How about a when posting a web link post (or comment?) there's a tick box/link that makes this easier (maybe opt in).
Not sure sites like archive.is have APIs or can generate or check for links via HTTP get/post but at least having a link to those sites would be nice reminder.
Giving any more traffic (which does help drive their value) more than we need to to people who hate us makes no sense.
Do not forget that these people want you voiceless, penniless, politically homeless, excluded from financial systems and the public square while trying to lock you in your home, and they think it’s funny