Because of the very nature of insurance. I am not singleing you out here, but I am surprised at how few people actually understand the concept of insurance. there are a number of ways for insurance companies to "insure" they make money. they can configure the pool of memebers they insure to those who are least likely to ever need to be compensated for their loss. (in the auto insurance industry that is called redlining). They can place caps on their payouts, both yearly and lifetime. But one of the best ways is to simply make the pool gigantic. At any one time only a small section of the entire population is in need of medical care and even more relatively rare are incidences of very expensive treatments. The majority of all medical expenses occur in the last few months of a person's life.
So, they can't figure out how to insure just a segment of the population without taxation - that is the reason for the manditory enrollment or taxation.
This is all the Heritage foundation's idea, I still can't believe that the right is so against something that is, in effect a support to insurance companies - and (perhaps) a boon to individuals.
And one more thing - this "the majority did not want it" spiel is nonsense. Firstly, it is quite obvious that "the majority" doesn't even comprehend their current, pre-obamacare policies, and they have been indoctrinated through all sorts of means. People still believe there are death panels for god sake. Secondly. We know for a fact that the majority DOES want gun control of one sort or another, but you are not willing to grant them this - are you.