No two are exactly the same.

Also, those premiums will get extremely high extremely fast with your method. People are already stretched thin paying for other people's payouts. If you're in good health, you would just opt out completely and that would raise the premiums even higher for the people who really desperately need it...

If healthy people stop paying in, and only the unhealthiest people have health insurance, that would nearly amount to cash pay for those with the worst conditions. You want to incentivize healthier people to stay in the game to help "subsidize" the unhealthy.