As reported earlier this month, a program in Japan that lets users download digital versions of their PSP UMD games to the Vita won't be offered in the US or Europe.

Why? According to Sony Worldwide Studios boss Shuhei Yoshida there just isn't sufficient demand to make it worthwhile for the platform holder.

Speaking in an interview with Wired, Yoshida explained that UMD transfers are more of an issue for Japanese gamers because the PSP has enjoyed much greater popularity there than it did in the West and titles are still being released.

"The system has been introduced in Japan, where there is a much larger demand for PSP games," he explained.

"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. So there is a lot more demand… to introduce a program like that."

Yoshida added that UMD games are much cheaper in the West than they are in Japan, and it won't cost much more to buy new versions than it would to pay the fee to transfer your existing discs.

"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," he said.

"There are many, many games that are sold at an affordable price. Because people in Japan are not getting the digital copy for free, because it costs us money to develop and maintain the system so we are asking people to pay somewhere between $5 and $10 to receive the digital copy in addition to what they have on the UMD.

"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."

The PS Vita launches in the UK tonight.