I find it rude because if I emailed them, it might be an FYI but requiring no action. If they just delete it, they might then be confused about project status later. I would be annoyed to have to re-send a message after the fact because they don’t think ANY email during their time off has value.
No one thinks much about cybersecurity while traveling. However, email security company Tessian warns the out of office message actually plays right into the hands of threat actors and cybercriminals. It’s a social engineering attack vector that no one thinks about. The out of office message is ubiquitous and handy. But if it includes any personal information at all — such as attending a funeral or going out of the country — attackers have all the information they need to impersonate the person who is out of the office, without the attacker having to do any real work.

I’ll also admit to not changing my voicemail for OoO in the past 3 or 4 years. I rarely get calls anymore it’s just not worth it… I figure if they don’t reach me by phone they’ve already emailed me or will email me after the voicemail.
I had a boss that required OOO messages anytime you left the office. A single sick day, leaving four hours early, coming in two hours late, etc. This at an org that didn’t require quick email responses, and at which people typically only put up OOOs for multiple days out.