US hospitals created entities to negotiate with the suppliers to get better deals for them. At some point they stupidly decided that these entities can finance themselves by taking percentage on transactions (as opposed to being financed by the hospitals according to entities needs as it was till then). Then the thing went downhill from there. Entities got free, became for profit, concentrated, and now they stand in the middle between hospitals and suppliers taxing the trade between them and punishing everyone that wants to get free by making deal with other business partners of that hospital/supplier more expensive.