I’m part time. I don’t use an out of office message, but I do have my hours in my signature, and sometimes include that information in the body of email. Many of the people I correspond with frequently need things turned around quickly – postings for public meetings need to go out so many days ahead of said meeting, and similar. They need to know when I’m available to get the work done!
I also tend to check my email 2-3x per day while I’m out for my own sanity and will respond to important* ones if not doing so would hold something big* up. Not using OOO avoids some of the self-righteous nonsense from people with nothing better to do than try to micromanage my personal time.

Then there was the occasional one who would do what Alison mentioned with the sickness excuses, and create a tale that read like a police report: “I must miss my deadline because, on the night of August 12, my 45-year-old sister was alone in her house when an intruder entered. He was a 6’1″ caucasian male wearing a black balaclava and carrying a candlestick. As my sister approached him, with the dog barking around her heels, she heard a distant car crash which led her to have a fatal … etc.” (This is not an actual excuse I received, just similar in detail to some of those that were submitted.) These ones I was pretty sure were a writing exercise, requiring time and effort that could have been put to better use on the actual assignment they had been given.
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