Steam was successful because it combined advantages for producers and consumers with minimal changes to the business model. The old business model is people buy games that come on a CD or DVD in a small cardboard box for $30-50; the new business model is people buy games that finish downloading in a few hours for $30-50. Not really much of a change in revenue stream.

Cable TV, however, relies on splitting up the channels people want into different packages, that each come with lots of channels they don't want. They also need to overcharge you so they can afford to cut the prices for the "package deal" (TV/Phone/Internet bundles). What people want instead is more à la carte options, with a discount from package deals because they're asking for fewer channels.

So moving to a service that would cut piracy would still hurt financially. Another advantage of piracy is that they can blame their financial troubles on "filthy criminals" and use that to extract some benefits from compliant government allies. Offering a less profitable service that reduces piracy robs them of that as well.