You're assuming everyone can navigate - I know they are supposed to be able to, I suspect there's plenty that can't though. Also, those escape routes you have pointed out require a rational mind to make that decision, then find some help somewhere else, then get in touch with the organizers to let them know what you've done...
Yes you're right, but not all who find themselves in trouble will arrive at those decisions. A group can be a pain in the arse, but it's safer for all concerned; in the event of an accident it means someone can stay with a casualty whilst two others go off to get help.
Maybe anyone wanting to go solo could sign a disclaimer of some sort, but I can't see it happening.