[r00fus]

Because a profit-based market only works if supply/demand is elastic. In the case of, for example, healthcare, it becomes extremely inelastic [1] - at some point, if your life is at stake you could be willing to pay exorbitant prices for what should have a lower market cost (ie, say, blood at the right time).

Key-to-our-survival is a very strong leading indicator that the demand curve can get inelastic - giving inordinate bargaining power to private enterprises whose entire charter is to get as much money as possible (which makes sense given a normal elastic demand curve).

Healthcare, Energy, and Food should all be places where regulation prevents extreme arbitrage, or those doing the arbitrage will eventually be the de-facto rule-makers. If you want to live in such a society, fine, but I'd rather not. Note: some say we're already at this point, which is depressing to contemplate.

[1] http://en.wikipedia.org/wiki/Price_elasticity_of_demand