Ever filed a claim with the AMA?
As much as a lot of places would like you to believe it, you cannot sign away liablity. Even if you sign a piece of paper a provider of a service, event management, shopping mall, etc can and in a lot of cases has been held liable for injuries or issues that they failed to anticipate and/or prevent. The insurance companies are the ones who have you sign a waiver or have signs posted. Just look at Ice Hockey. They had it printed on the ticket that it was dangerous to be in the stands. People got hurt and on at least one occasion got killed. The owners and the city where held liable even though they put up warnings. Why because they didn't put up barriers or nets to stop the puck. Now they do in most venues.
Who paid for the litigation? Insurance!