Health insurance is not a luxury. It is a necessity.
A mandatory plan should avoid the problems of adverse selection that are crippling the GM health plan (an older and older insured group costing more and more in benefits) by including the young and healthy. It would also not shackle workers to their existing jobs. Ever heard of something called "pre existing condition" ?
1. This country existed for about 170 years without it, so I'd hardly call it a "necessity."
2. Even if it were a necessity, there's no reason for government to mandate it. Eating is a necessity, but any so-called "leader" who sponsored a law mandating a minimal caloric intake and maximum fat content in everyone's diet would be laughed out of office.