If there's one thing I learned working in IT it's that devs actively half-ass their error messages, routinely misspell critical words you're gonna grep for in logs, and never even consider having someone in Product read over customer-facing error messages like this. All they see is a Jira ticket that says "include the following verbiage in the VPN rejection message" that was typed up by a mostly plastered PM one afternoon after they downed 3 margaritas at "lunch" at the taqueria next to their office. And then they just copy and paste that shit into whatever bullshit HTML template took the least effort to find.
Error pages are a point where something bad happened, so the user is already in a bad mood. A shitty joke just makes the situation worse.
The only time I can remember enjoying novelty error messages is for 404 not found pages. It's usually stuff like the Google T-Rex thing, or I've seen an astronaut floating in space, stuff like that.