However, please stop equating 'loss of potential sale' with simple theft. Clearly, if I take one of your DVDs, it is lost to you. If I copy a digital file of the same movie, you still have the use of your own copy.
Now from a publisher's point of view, what TPB is doing is not so much depriving them of movies or other content, but interfering with their right to bring it to market at a price of their choosing - if the same software is easily available for $0, there is little incentive to purchase it. (We can argue about whether the purchase would ever have taken place; eg if a student downloads some high-end 3d modelling software to learn how to use it, but that's been addressed elsewhere.)
This is an extreme case of the ongoing economic struggle between publishers and distributors in general.