One thing I've been curious about is whether insurance companies are useful as negotiators with healthcare providers. At the end of the day, they are for profi

One thing I've been curious about is whether insurance companies are useful as negotiators with healthcare providers. At the end of the day, they are for profit enterprises. The cynic will naturally state that they make money only by denying claims while taking people's money. But were I in charge of such an enterprise, only doing that would leave a lot of money on the table since there are still lots of claims that an insurer is still paying out and there is a strong economic incentive for insurers to bargain aggressively with healthcare providers to get access to the pool of healthcare customers they represent. With this in mind, does anyone familiar with the industry know the impact insurers have on bringing down healthcare costs by putting the squeeze on healthcare providers?