They might feel it's worth it to lose that money in the short term if they can make an example out of pirates and try to establish account termination for unproven allegations of infringement as an industry standard practice. Long term it isn't smart but there are media industry mouthpieces claiming they will be losing $52 billion to internet piracy by 2022. How many DSL customers will they be willing to drop if they think it'll help stop the billions their parent companies are "losing" annually.