Consistency
In light of the recent membership announcement, people in the SCA have been asking "What do we need the corporation for, anyway?"
Consistency. Do you want to belong to a multi-national organization that has members around the world, all playing by (basically) the same rules? Do you like going to Pennsic, and Gulf Wars, and Estrella, and actually being able to participate without having to change everything you do? Then we need a corporation (or some governing body-a corp might not be the only way to do it) to cover that.
I believe it is true, that if the current SCA, Inc., were to fold* there would be local groups that would spring up to take it's place, and people would continue recreating history. But I think it would quickly devolve into "our game, our rules" and become very parochial. To be fair, a lot of people wouldn't mind that. If you aren't doing any inter-kingdom activities, then it probably doesn't matter.
What do I think needs to happen? I think we need a full-time executive director to run the place. Think what we could be if we had someone whose job was to actually address the issues of member benefits, fund-raising, marketing, putting out a really high-quality magazine for reenactors.** We can do a lot with volunteers, but I believe the corporation is stagnate because there is no one dedicated to moving it forward - and therefore, the biggest thing it does for us is to provide the umbrella of rules under which we all play.
*I don't know that this particular crisis will cause the corporation to fold, but for a long time I have thought it will be a lawsuit that will bring it down. This might be the one.
**This is not to say that the corporate staff, officers and/or the BoD are ineffective, or incompetent, or that they don't make efforts in this area. I believe that, more than anyone knows or believes, those people put their heart and souls into running the SCA. But by the nature of the work they are more frequently responding, not looking forward. There isn't really anyone to look ahead.