I’m out of town. I’m looking forward to connecting with you when I return. If you’re getting this note, it means that I’ve received your email. (Thank you!) I’ll respond to your note as soon as I can. In the meantime, here’s a list of five questions that I get asked often. I’ve included brief answers to each one below. Take a peek. You might find the answer that you’re looking for—right away! [Include brief FAQs here] I hope those FAQs were helpful. Don’t worry, though—even if your question was one of the questions listed above, I will still send a personal response to your note as quickly as I can, just to make sure that your question or problem has been completely resolved. Talk to you soon!
I wonder if anyone ever calculated how much time was wasted producing those messages.

Usually, people take leave for vacation, business traveling, maternity leave, or sickness. Additionally, sometimes employees who will no longer work in a company also need to provide an out-of-office message for their customers, especially if they are in a high-level management position working closely with those customers.
I once left a kind of breezy, fun out of office message for “people inside my organization” that said the literal truth: “I am out of office this week at a mountain resort where I have paid many hundreds of dollars for someone to take my electronics away from me. I’ll get back to you Monday,” and a very normal and professional OOO for “people outside my organization.” Needless to say I returned to a message from a senior (but not, I stress, my boss or even on my team) colleague calling me out on it. People surely can make things their business.