I once thought this is a cool idea . . . and still could be for others. I rode along with a small group one time for one of these events, and thought between ear plugs and helmet, all would be o.k. Once we got to the staging area in the North parking of the Pentagon, it was clear there was a way in, but no way out. And the noise from the loud pipes crowd was uncomfortable. We bailed out before the trap closed. Stories later of what we'd missed were mostly negative. Four-hour wait trapped in the staging area was common (takes a long time for many motorcycles to pass through a small opening to form a line) with no facilities. Widely varying rider capabilities combined meeting bad spots in the road and crowded conditions limiting avoidance options led to a number of folks going down.
You get the picture . . . yes, it can be a good cause . . . those pesky details.