People don't think or listen
I am part of the club that was helping WSA Pro Ice put that race on. Our club members instructed the drivers of those rigs of what the ice thickness was and instructed them to park farther apart from each other. Obviously, they didn't listen to us or think for themselves. Everytime there is an event around the lake there is plenty of off lake parking, however everyone wants to be on the ice and they make thier own choice.