It's hurting Comcast's TV business, not Comcast's ISP business. But they try to rip Internet users off to compensate for their declining TV profits (because of very poor competition and monopolistic position of Comcast as ISP in many places). That's exactly what they are doing by jacking up Internet plans prices, pushing nonsense data caps and so on.

They admitted as much themselves: https://www.mediaplaynews.com/comcasts-solution-to-video-sub...