Bon voyage! You’re going on your holidays and you’re completely leaving the office behind. This is the perfect auto-response if you won’t be checking your emails the entire trip.
Out of office messages can also make your workload easier when you return to the office. Colleagues and clients who know you are on vacation or at a conference might be less likely to fill your inbox with messages. If someone does need immediate help on a project, they can know who to contact in your absence to make sure it gets handled on time.

Again, this will depend HUGELY on what sort of role it is (an external-facing vendor, for example, should probably not use something like this). But for many internal requests, it is not power-tripping to ask someone to either redirect their email or wait until a later date to send it.
When one of my colleagues went on vacation, he sent an out-of-office message that was both clever and smart. First, he sent the recipient on an imaginary scavenger hunt to "the highest peak of the tallest mountain." He used humorous absurdity to make it clear that he would not be checking email while he was away.