When the PlayStation Vita was formally announced, people were very aware that it didn't have a system in place to play UMDs. Sony were just dropping support for the last generation handheld and that rightly annoyed those people that had spend hundreds of dollars on PSP games.
So the Japanese solution was the lesser of two evils: register the game and get a discount on the digital version. You still had to pay for that second version, but not nearly as much as you would have done otherwise. Gamers grumbled no end and then began to grumble even louder when the scheme was ditched in the west. Why would Sony apparently go out of there way to annoy western gamers?
"I’m sorry we are not doing it in the States," Shuhei Yoshida explained to Wired. "There are two factors that contributed to the decision as I understand it. I’m not in a position to make that kind of business decision. The system has been introduced in Japan, where there is a much larger demand for PSP games. When you look at the release schedule of new titles there are still lots of PSP games being released in Japan and being announced for release. Lots of people who are interested in trying Vita are also interested in playing PSP games that they might purchase before Vita comes out, and will not necessarily choose the digital version."
"The other point is that when you look at PSP titles sold digitally in the States or Europe, games are sold for a really reasonable price. You can buy Final Fantasy Tactics for $10. That’s a great price. When you compare that to the price of games here, PSP games in Japan are sold at a much higher price, so people see the value in spending the $5 to $10 to get the digital copy. But when the games are already sold at a lower price in the U.S. we see less value in introducing that kind of system."
