Well, you can't, because of defined enrolment periods and coverage delay periods, and that it's impossible to tell ahead of time whether given insurance covers

Well, you can't, because of defined enrolment periods and coverage delay periods, and that it's impossible to tell ahead of time whether given insurance covers a given condition. In addition, medical insurance makes no sense as a risk-pooling strategy, as everybody consumes some medical care annually, and the average cost of care consumed is greater than the amount most people can pay. There has to be something else going on.