You ask a very interesting question. Have you ever noticed that individuals are often charged and convicted for having porn on their computers but NEVER do you hear of the porn sites who sell the porn being charged?
The sellers have big $ to fight any charges. The individuals do not so that the prosecutors stay away from the sellers.
It's always about $ or lack thereof.
You're speaking of child porn, right? Adult porn is not illegal.
A great deal of the child porn on the internet is hosted overseas, out of U.S. jurisdiction.