Oh you see, I do that on purpose. That way I can use the same OOO message internally and externally. Anyone within our company can find us in the global address book. Anyone outside our company who has done business with my department has my email address & my manager’s.
By making this information public, you have unwittingly given a hacker everything they need to complete a Business email Compromise (BEC) scam. In these BEC attacks, the hacker commits fraud by pretending to be a senior employee and will attempt to coerce the recipient into complying with a fraudulent request – such as wiring company money.

Also, you need to know your audience if you are going to go eccentric. Alison mentions that this message is fine in their culture, but it wouldn’t npbe appropriate for my somewhat formal field. And even if your workplace in general is casual, you might be contacted by someone outside. (In a tiny provincial courthouse I served in the past, there is a story going around that in the 80s a junior but elderly clerk used to address phone callers as hun and sweetheart and generally speak very informally. Most people thought it was funny, and then the President of Supreme Court called and… he didn’t).
But what if you’re only taking off one day? Sometimes, it might seem silly to bother with an out-of-office for such a short amount of time–especially if it’s a day that a lot of other people are taking off (such as a national holiday). If people do need you to get back to them urgently, they’ll think they’re being ignored. (Even if you define “urgently” differently.) And if there’s a chance of an emergency landing in your inbox, it’ll be that much harder for you to unplug because you’ll just keep “checking in.”