One potential difference that I see is the PERCEIVED value of US Sailing membership from catamaran sailors, as compared to other athletes and their national organizations (as in the cases you mentioned).

Personally, actions of US Sailing often leave me feeling that we (catamaran sailors) are there for them (membership dues), rather than US Sailing being there for the good of the ENTIRE sport of sailing.

If I only sailed monohulls, I would join US Sailing based on your premise.

If there were an organization that I felt truly represented all catamaran sailors, I would join and would encourage others to do so.

If you sail at Alter Cup, or at a nationals, I agree you may benefit from the race official training and/or other aspects. What about all the sailors that dont race at that level? Our statewide regattas dont require certified officials, nor do our fleet races. I look at it from an individual basis. If your racing at a level that you think US Sailing is helpful, then join and support them.

In short, too many catsailors dont feel that US Sailing IS their national organization, so its not a fair comparison to other sports.