You don't wear a helmet because you suck, or are a beginner. I wear a helmet every time I ride so that I don't crack my skull and die, or worse end up having to wear diapers and get tube fed all my life while consistently slobbering.
Right I know, you have a style, and "Yo, I can't lock into my steeze with a lid, bro..I need to feel free." Don't you dare be that guy. That is the lamest thing any real snowboarder, or human for that matter has heard. Just get used to it and expand your steeze. At a minimum it's more sticker space. You are doing it for yourself so that you can ride tomorrow, remember that.
Now if you don't wear one because in all honesty you can't afford one or it is not in the budget you are lying. A one day lift ticket is more expensive than a lot of helmets out there. So is a night at the bar. Next time you see a helmet for a wicked deal think about that.
I've experienced two concussions, while wearing a helmet both times. I had a headache that felt like a boulder was using my head as a punching bag for a week. Not cool. I was lucky, because I think to myself, what if I didn't have a helmet? Well pretty much every day of riding after that might not have happened. Scary, but that is the truth.
If you are boarder that people watch, and especially if you are taking shots and video, wear a helmet, because kids love you. Knowing little Maxwell is sitting in a hospital saying "but Your Name Here doesn't wear one probably won't feel to great.
"Let's all stop making excuses and live to ride another day"