Why can't europeans get the standard DS cases? Is it they can but they just have import fees too high?
It's because if you want the original US DS cases you have to buy it through a middleman since Nintendo Of America doesn't ship to Europe. So you have to find someone who buys the cases for you and then resend them to you. This is a matter of trust as well as money as you have to pay twice for shipping, once to your middleman and then from him to wherever you live in Europe.
The same goes for EU DS cases. Only Nintendo Of Germany has them, so again you need a middleman. Apart from that EU DS cases are clear instead of black and they have a wider spine. That means after all the hassle to get them to your doorstep you'd have to modifiy the coverimage to fit the new measurements.
With all these obstacles in the way I can see why one is considering DVD cases as an option because they are available everywhere, cheap and in bulk supply.