Because Obamacare does a lot more than just insure more people. Though for those newly insured, it has improved their healthcare by funding what couldn't be bought before, already proving you wrong.
Obamacare also requires insurers provide contraception for the price of insurance premiums, which is preventive medicine that reduces costs due to unexpected pregnancies and STDs.
You're pretty sure that health insurance is meant to cover only catastrophes, but it's not. It's to cover spikes in health care costs that come from occasional expensive events. It's just like car collision insurance: it's a financing strategy that allows people to keep moving through life in a way they can afford, based on statistics. In fact car insurance should pay for routine maintenance that prevents catastrophic costs like engines seizing or bald tires skidding into something.
The financing costs money to operate, plus salaries and profits to motivate people to dedicate the time it requires to do it properly. Though not as much as the insurers charge (up to 20% of premiums, even under Obamacare). What every one of our foreign competitors has chosen over the past several generations is a public health insurance system like unemployment insurance, which we already have for a lot of Americans in either Medicare, Medicaid, VA insurance and some others.
In fact you have called for public health insurance in what you have detailed. Except for some reason you want an "employer offered health account". Why should the employer have anything whatsoever to do with health? Why should an employer even know when you have drawn on payments for medicine? Why should you have to move it when you change employers? Why should employers spend one minute administering health financing when their business is totally unrelated? Obviously that "account" should be Medicare/Medicaid/VA insurance, paid by taxes, administered without profit by the government that already does so very well for many millions of Americans.
What's wrong with you libertarians is that you cannot accept that government is the people joined together to protect ourselves, at a great scale economy. You're obsessed with authoritarian private corporations that demonstrate daily the vast waste they layer atop most widespread services, especially those that are equally available to all. You reduce actual life experiences demonstrated everywhere to inane sloganeering like "heading down the path of communism, and history has already told us how well that works". No, you have merely cherrypicked history and called things names without regard to their meaning.
There's more to economics than economics 101. There's more to reality than the libertarian mayor of Sim City bothers to carp about.