Others have pointed out that authors won't get paid that way. But I also disagree that it is faster or easier to pirate. First you have to have a decent source (or multiple sources) to search for the books, hope that they are decent enough quality, hope that they have enough peers that you don't have to wait a day to download the book, etc. By contrast, on Audible you press one button to buy and another to download. Even when you take into account any DRM removal, the necessary time and effort are much lower.