When done correctly, the banner is actually a consent banner. It’s a legal thing, not necessarily trying to discourage criminals. It’s informing users that all use will be monitored and it implies their consent to the technology policies of the organization. It’s more for regular users than criminals.

When it’s just “unauthorized access is prohibited”, though, especially on a single-user server? Not really any point. But since this article was based on compliance guidelines that aren’t all relevant to the homelab, I can see how it got warped into the empty “you no hack” banner.