The further those services get pushed down, the less effective they become. With smaller groups to front costs, prices go up and less services are offered.
Arguably that militates against treating it as insurance as opposed to a straight-up single payer system or Singapore style system (http://theweek.com/articles/684952/republicans-should-blow-e...), but it does mean you can't argue from the success of existing insurance markets.
Even now, there are places like https://surgerycenterok.com/ that prove high quality healthcare can be provided at affordable prices (they even list them on their website!).