Not essential by any stretch.
I’ve been skiing, racing, doing stupid steep stuff off piste for years, and never had a head injury (not to say it couldn’t happen)
Used a helmet for racing and occassional steep stuff.
If you feel better wearing one then great, but I reckon it gives people more of a FALSE sense of security.
I was knocked flying once, probably about 30m through the air, didn’t touch my head, but ribs hurt like hell and twisted knee.
Personally I would be more concerned about improving technique and having bindings that release correctly