Helmets are good. It’s my opinion that upper-body injury, including head injury, is more common snowboarding than skiing. High-speed collision on busy pistes kill people and colliding with trees and hardware kills too, while getting clonked on the head when dismounting a chair lift can merely ruin your day.
Ski helmets seem expensive. Until recently I used an inexpensive but sturdy jump-bike helmet ~£20, together with a stretchy tube-scarf to cover my ears. An XC helmet has too many vents to be comfortable IMO.
But I recently got a proper ski helmet from Aldi for £25, and it’s quite nicely designed too. If you can’t get one, I recommend the jump helmet and scarf method.