Well, is that the people who bought the phone at fault or MR members who are jerks?
We have some older family members who have older phones. My inlaws and my grandma in law have 5c/5s phones. They know not to upgrade to the new OS and they don't really need it. No complaints. They'll probably get some newer phones this round from us (the 6s and 6 SE models we're upgrading from... my 7 plus and my son's 7 plus will get sold) and my inlaws will then move up a little on OS, but not to iOS 11 on those. Nope.
It helps them to get these phones from us. They're on a budget and phones aren't their top priority. My FIL's is his golf game, even though he loves gadgets and would probably dig my 7 plus.