Hey! We already did. Back in the early '90s there was one newsgroup for all skiing related discussion, it was called rec.skiing. As the group became overwhelmed with too many topics several people worked hard to form additional groups, at the top of that list was Crispin Cowen. After much discussion and voting the current hierarchy of newsgroups was formed. And why, you ask, is it called REC.SKIING.snowboard? Because it was more technically feasible to do it that way when rec.skiing was split up. It is the way it is and it would take a lot of work to change it, so unless you're willing to do the work don't even suggest it.
There is another snowboard newsgroup called rec.sport.snowboarding but its not a legal group and is not propagated very well. What this means is that the group was created without going through the formal voting process. A few machines on the net still have it listed as a valid group but it isn't.