Answer:
Copyright is as much an ethical concept as it is a legal concept, primarily because it's very rare that anyone "gets caught." Because it's so easy to find, copy, and distribute infringing material, there's no way for the legal system to prosecute everyone; society relies on an individual's morals to convince him or her to "do the right thing."
It's also frequently forgotten that when infringing a copyright, while it seems like you're only hurting Sony or Paramount--big, faceless companies who won't miss a few cents here and there--you're actually interrupting the revenue stream of the individual artists.