Because this would enable Comcast to then increase what fees it charges Netflix, higher and higher, until either Netflix says "that's enough", and don't pass on

Because this would enable Comcast to then increase what fees it charges Netflix, higher and higher, until either Netflix says "that's enough", and don't pass on that increase, or Netflix starts losing customers to say, a cheaper competitor that Comcast prefers because it owns (part of) it. Better stop these games at the door. Most Comcast customers don't have a choice of provider anyway, so it's not like they can choose a different ISP to connect to Netflix. You don't want to penalize customers stuck buying from a monopoly. Other customers paying $8/month to get this amazing Netflix service and are "forced" to "subsidize" Comcast customers, that won't elicit much tears from me. :P