I think it does hurt. Some wouldn't buy anyway. But the mindset has changed.
If you do the right thing, you're out say $30 for a book. If you do the wrong thing, you get the book and still have your $30. Some people don't care about others, and that mindset continues. (its kinda a Tragedy of the commons where the "common" is the market place https://en.wikipedia.org/wiki/Tragedy_of_the_commons).
DRM makes it worse, not only did you do the right thing and buy the book, now its not as useful as the copy someone "didn't pay for". So pushing people toward the free and better.
If you do the right thing, you're out say $30 for a book. If you do the wrong thing, you get the book and still have your $30. Some people don't care about others, and that mindset continues. (its kinda a Tragedy of the commons where the "common" is the market place https://en.wikipedia.org/wiki/Tragedy_of_the_commons).
DRM makes it worse, not only did you do the right thing and buy the book, now its not as useful as the copy someone "didn't pay for". So pushing people toward the free and better.