In defense of boarders:
1) Most people have to sit at the top of the run to strap in. Just like most you skiers have to stop and adjust your gloves/hat/poles.
2) Standing up while stopped is tiring on a snowboard. Its easier to plop your butt down somewhere while waiting for friends higher up the run catch up. I see skiers standing still all the time in the middle of runs to wait for their friends to catch up.
That being said... both parties need to be courteous about it and not block the runs. When big groups ride together with varying skill/speed levels this ALWAYS hapens. And its annoying. Personally I hate riding with more than 2-3 people. Also I have Flows so I don't have to stop or sit to strap in after getting off the lifts, which my skiing friends appreciate.
Also I've ridden east/west coast pretty extensively, esp in the NW and NE. East coast mountains do not compare in any way to the sheer magnitude and massiveness of west coast riding in terms of snow amount, bowls, elevation, etc. That being said the NE has some great terrain when they get massive snow dumps (ie a Nor'easter) a couple/few times a year. And while most of the time the snow is heavily groomed or ice, I had some amazing times at Sunday River, Killington, and Jays Peak. Also on the east coast you do get alot of riding in clear sunshine weather which is very rare on the west coast.