[blueskin_]

>there's a simple remedy- Don't scream "help! anyone! help!" scream "Hey you, burly looking dude. Help! yes you!"

Exactly this. The same goes for calling emergency services - there are cases where response was delayed because everyone was assuming someone else was doing it. I've been the one person who did it before, I'd say due to having an understanding of this. It's really something people should be taught about in school and how to avoid both participating in it and letting it happen.