This was a stupid law. Hell, the govt wants you to gamble on the Lottery because "it's for the children" but don't want you to play online poker? Stupid, very stupid.
And you don't get the connection? Government regulates gambling. Maybe the shouldn't, but they do. If you are going to regulate gambling, you need to make sure you regulate it for everybody. The state lotteries don't want to compete with private enterprise, so governments regulate state-by-state what private gambling companies can do.
But the internet crosses state boundaries, so the U.S. LONG AGO made it illegal. But they haven't been able to control it, so they passed this law to cut off illegal payments to the companies running illegal gambling operations.
So be mad about government regulating gambling if you want, but don't attack the congress for simply making the playing field level given the current regulations.
The reason was very simple and one not mentioned in this article. Most of the online gaming is offshore and I've read the government had some proof it was helping fund terrorist groups. Good reason IMO to ban it.