If the owner of the file makes his living by selling copies of the works he created, taking a copy and putting it on the web (where they can be had for free) reduces the value of his works. In other words, the owner is deprived of the use of his works because you've diluted their value.
The argument that "you still have the original so you are undamaged" is false. If the startup you work for dilutes your 5%=100shares of equity down to 0.0001% and the value of your stock is reduced to near zero, I can asure you, you won't feel comforted by the fact that you still have 100 shares.
Shares are different: they're like money, they represent value. A copy is a copy. Humans copy: that's how we made technological progress. Someone didn't invent agriculture while out on a hunt and then coast for the rest of his/her natural life on the "intellectual property" and then have his/her descendants coast on the proceeds. People copied what they saw that worked. Copying is how humans make progress, trying to stop or inhibit that is going to warp society beyond belief.
The argument that "you still have the original so you are undamaged" is false. If the startup you work for dilutes your 5%=100shares of equity down to 0.0001% and the value of your stock is reduced to near zero, I can asure you, you won't feel comforted by the fact that you still have 100 shares.