I think that’s maybe something you need to deal with internally with the person/people who you’re asking people to speak to instead – I think if you start to ask the original sender to update you or cc you then it’s going to start to annoy people that they are doing the running around, plus not everyone will do it.
There are a million reasons why people feel the need to sheepishly telegraph that they’ll be checking email while OOO: a toxic workplace culture; a set of bad managers who don’t model work/life balance or use manipulative tactics like saying, ‘feel free to take some time if you need it’; companies that are so focused on lean growth they don’t have anyone to pick up the slack when an employee opts to take time off. These days, merely having the confidence to step away from your job by taking the vacation time granted to you in the terms of your employment agreement is still a privilege in the American workforce.

Or, worse, when someone has left the organization and the organization hasn’t bothered to put up an OOO, so I’m just emailing a blackhole until I call or someone finally checks that inbox. I never fail to set up my OoO reply, and yet most of my external contacts don’t get them. Let’s say I work for LlamaCombs, with an name(@)llamacombs.com address, and this is a company who has two clients AlpacaBrush and VicunaShampoo. I work primarily with the second, and their internal directory lists my contact info as name(@)vicunashampoo.com. It works because any e-mail sent to the second address is auto-forwarded to the first. Except it messes up OoO replies big time. Because the auto-reply is sent to my own alternate address, not to the original sender, and I have no way to change that.
“Ideally, an OOO should include the basics,” says work and wellbeing psychologist Kate Sullivan. “The dates you'll be gone, an approximate timeline for when someone can expect to hear back from you upon your return, and how any urgent requests will be handled in your absence.”