It detracts from the ratings. Unlike movies, where they claim torrents steal money from their pockets, shows depend on their viewers. The more legitimate viewers they get, the more likely the show will stay on the air. They can watch the viewers on TV, adding in +3 and +7 for DVR counts, and find out how many times it's been watched on iTunes and Hulu, along with other websites. What they can't count is how many people have torrented the show. More people torrenting mean less people being counted, which means lower ratings, which means cancelled shows. Torrent may be great for people outside of the country who won't see it, but within the viewing areas (in this case, US, Canada, and the UK), it hurts more than helps.