It's a recruiting and screening tool. By having one of these gatherings every time a cause comes along it allows fellow travelers to congregate and renew acquaintances and share information.
It also recruits useful idiots to the program. The confusing and contradictory demands of the cause are a screening tool to make sure only the real idiots join.
Correct assessment of the situation with these protests & the truly sad part is that so many of this nations college kids are falling for it.