They could only cut out the middle man if they built their own global network; they don't have any fiber running to Europe or Asia or elsewhere. If there were no middle man, Comcast customers could only reach other Comcast customers.
But they are cutting out the middleman with respect to large traffic sources. Netflix won't be the only one to pay for an interconnect; AWS, Google and Facebook will likely follow suit shortly. Take that business away from the transit providers and it hurts.
