Earlier quoted context omitted.
The mandate is what prevents this. The only failing is that the penalty was too small.
Really, there should be a default (probably public, but perhaps just the lowest-cost bronze plan you could buy off the exchange) option, for which you pay the premium, rather than a penalty. If you want coverage to be mandatory, make it really mandatory.
That seems like a good solution. Or, of course, stop pretending it's market-based and start taxing people for it instead. Unfortunately, the ACA had to be watered down a lot just to get the more conservative Democrats to accept it.