Because copyright infringement has been linked to theft, which means people view it like they would view a theft, and it thus appears completely harmless because people place the entire negative of the theft on losing the item. Imagine I had a magic power to duplicate any items, went to a friends house, and duplicated his TV. No harm to him. If anything he benefits a bit because when he is at my house he now sees the bigger TV.
Most people don't realize there is a victim in my example. The person who I would've bought the TV from. Except they are far less a victim that someone who has their TV stolen. Because I may have instead just stuck with mine and never gotten a bigger one had I had to pay. The problem is that when aggregated accross the whole population, lots of people who would've bought one now don't, and that is where the damages come from. Of course, the big players in copytright claiming the extremely high numbers for their damaging only work to further get people to dismiss this line of thinking.
Most people don't realize there is a victim in my example. The person who I would've bought the TV from. Except they are far less a victim that someone who has their TV stolen. Because I may have instead just stuck with mine and never gotten a bigger one had I had to pay. The problem is that when aggregated accross the whole population, lots of people who would've bought one now don't, and that is where the damages come from. Of course, the big players in copytright claiming the extremely high numbers for their damaging only work to further get people to dismiss this line of thinking.