Comcast should care if comcast loses business. But as you stated that doesnt seem to be an option for a lot of people. Thats the "advantage" of a monopoly for you. And termination fee's for a isp contract seems ridiculously high. If I needed to cancel my subscription i would have to do it 1 month in advance and thats it, no other costs whatsoever. You can try to put pressure on SE but i wouldnt hold my breath for them to respond.
As a suggestion you dont have to cancel subscription early, just give them notice that you are canceling when your next subscription term is over.