If you work for a company with a lot of employees it's usually a lot cheaper than individual insurance since it's negotiated and the employer usually pays a portion of it.That leads to the answer "Get a job that offers it."
Which leads me to the following:
Why should an employer be responsible? They have enough costs already so why should they be burdened with more costs? A big corporation with a very big workforce is going to be faced with a huge bill for health insurance if it's included in a labour contract. Of course those costs are passed on to the consumer which means if you buy a Chevvy then you're paying extra so that GM can pay for the health insurance for the UAW members on its payroll.
I would argue that spreading the cost on a social basis is far better. Toyota is a much more competitive auto corporation than GM because, among other things, it's not burdened with a massive health insurance bill for its employees.
I can actually address this. Employers became responsible for providing health insurance as an employment benefit because during WWII, government took control of wages and limited the amount of money an employer could offer to entice new applicants. Employers therefore had to start offering other incentives. The government then cemented the plan in place by making it tax-deductible for the employers, a perk that individuals do not get if they purchase their own insurance.
There is no particular reason that it must continue to be done this way, except for the fact that people have become accustomed to it, and are unable to fathom doing things a different way.