I still don't understand - even if the cost is literally zero to copy, that still wouldn't necessarily entitle one to someone else's work without compensation if that is what they require.
For most people it comes down to trying something they aren't sure they will enjoy. If you're not sure you'll like something that costs a significant amount and piracy is not an option, you most likely just won't buy it. If piracy is an option, maybe you still don't buy it, but now you get to try it. Both outcomes have the same effect on the publisher of the work so the act of piracy hasn't harmed anyone, costed anyone anything, and now the user can come away knowing whether or not they liked the work which is a positive. It's not that hard of a concept but easy to be confused by if you look at it from the traditional sense of physical wares where a "stolen" sale causes harm.
I think people consider a copy of work differently than the original in some abstract sense. Digital is the first medium that makes the copy equivalent to the original.
