I've heard it explained that "hey" used to be more of an urgent way to get someone's attention, rather than a casual "hello" like it is now, so it sounded rude to some older folks.
"Hej," pronounced "hey" is Swedish for "hello." Also "Hej hej" these days if you want to be more casual. It seemed weird to me at first, like "Hej mormor," for "Hello, grandmother," seemed informal, but if I said, "God afton," (good afternoon) my cousins said I sounded like a government issued language tape.
I remember my mom getting uptight over the word "sucks", as in "that sucks" or "it really sucked". Literally everyone was saying it, there was no way I could help it lol
A few years ago a very boomer gen-xer tried this on me and got very enraged when I would say "hey" instead of "hello {his name}". At one point even threatened me.
This reminds me of that old joke "what do gay horses eat? Hay hay haaaayyyyyy" that was told to us by a teacher in I dunno, middle school probably. Gotta love the 90s
Remembering how common it was in like the early nineties for a kid to say "hey" and some old timer to respond "hay is for horses!" as part of some campaign to label "hey" as rude and force kids not to say it. They're gone now and we still say hey. You lost, old timers.
Oh wow, so really we were giving them a mild heart attack, every time we were saying hi? I don't know if that really justified the grammar police (not using that other word casually, anymore) but also these are the people who created boomers, so they definitely had to have some issues they were never able to work through.