Short version... we have an insurance system which in response to WWII price controls, employer provided insurance has such a favorable tax situation that the individual market has a hard time competing... also you also have 50 states which each individually regulate insurance plans to the point that it is virtually impossible for someone in the individual market to shop around for a plan... let alone receive similar tax benefits.
Think about it... today you can hop in the car and drive to the next state to buy a car or tv, or even order that same item from an out of state vendor and have it shipped to you. Why can't you do that with insurance (of almost any kind)?
The answer is in large part because of state mandates and authority on policies. Even under Obamacare... your only option (on the individual market) will be to buy insurance from state run 'exchanges'... most of which will be offering a fairly narrow band of insurance plans from in-state providers... rather than allow consumers to shop around and get the type of policy they want, with those covered items that they care about.
Many things could have been done to improve the health insurance/care/etc system in this country... alas they took the chance they had and made things far far worse instead.
To go back to what I said... even if you remove Ohio from the list of states that ratified the 16th amendment... Delaware would no longer be the 36th, New Mexico or Wyoming would... both of which ratified it on the same day as Delaware. Not to mention New Jersey the next day, and Vermont 2 weeks later... all before the proclamation of it having passed.