It's important to remember that legal systems have humans in them, too. It's one thing to read a law, spot a loophole, and exploit it relative to what a hypothetical law computer[1] would say the law is. It's another to see a loophole, exploit it, and convince a human that what you did is not covered by the law.

Yeah, sometimes it happens, but I think we hear about it when it does because it's news. Much more likely, somebody's going to jail anyhow with your scheme. Judges are not stupid, in general.

1: You know, this guy: http://futurama.wikia.com/wiki/Computer_Judge