Removing that layer of indirection would make it your own choice to pick a provider, and the provider is then incentivized, at least a little bit, to provide you with a good outcome or else you may freely switch to another provider.
There's also the component that, right now, you lose the discounted group rate insurance premium as soon as you lose or leave a particular job. Putting the purchasing power with the end consumer means that you can keep your provider at the same premiums even if you switch jobs. All that might change is your employer contribution.