I use "we" because I want to get involved and help.
The competition ask for observers when required, no one asks for help with clearing up. I haven't been asked to help set up. You might argue it's initiative or common sense, but simply, we cannot go around expecting things to happen without asking.
Make it all the riders duty to clear up after a comp give yourselves a break. I am sure it would be done, when people are asked politely no one would say no. but if you just expect, then I do not think you can complain when it doesn't happen. Everyone has different expectations and I am sure if riders were told to expect to have to clear up you wouldn't have this problem.