There would be more chiropractors. Beds would be faster to make, and probably look better - nice and flat. The whole pillow placement issue would be gone - do you stand them up, do you lay them flat? Pillow fights wouldn't be a thing - and neither would the enduring male fantasy of nubile females in pyjamas jumping on beds hitting each other - sorry about that. Snoring levels would increase dramatically, leading to a higher divorce rate, a plummet in the sale of double beds, and earplugs being sold at a premium.

Pain and insomnia and more butts to sleep on.

Hay would be back on top

if they didn't exist, someone would have invented them, if they were banned, people would buy them on the black market, mobsters would take over and kill over the underground pillow racket, it would essentially be Prohibition all over again

You can use little wooden supports like in old Japan, which after a short while can replace your pillow. But people refuse to adapt to change and want stubbornly back into the fifties or whichever area they deem to be "best". For me the 50s is an era where Tyrannosaurus Rex stomped through people for dinner, so nothing I'm looking back to in desire.

Have you seen the ones Egyptian royalty used? They don’t look very comfortable.

Maybe it would help my back

People would have a slightly less fluffy personality.