Snowboarding socks are thinner, probably because snowboarders tend to sweat more and so they need to dry quicker. (I think the term is 'wicking'?)
I do know that my son who wears ski socks in his snowboard boots has wet socks (and cold feet) every evening, whereas his sister who wears thin snowboard socks has warm and dry feet at the end of her day...
The same reason is given as to why snowboard gloves are different to ski gloves (and yes, there is a difference).