You still don't understand. If Nintendo had done it a different way to start and made it so that the consumer could transfer purchases to a different DSi, you either wouldn't be able to copy stuff onto an SD card at all, or you would have to connect to the Internet every time you wanted to run DSiWare so that it could authenticate. Nintendo would not make the DSiWare platform without a DRM scheme in place, which removes any other possibility for how it could be set up.
With how it is right now, you don't have to connect other than to download software - meaning you can actually, y'know, take advantage of the portability of a handheld - and you can back it up onto an SD card, and the tradeoff is that the software is keyed to the hardware and can only be transferred over using developer tools (and do you really expect any of the console developers to give those to the consumer? This isn't PC, after all). Stop complaining that Nintendo is somehow at fault for "making you rebuy your games" if you want to go spend $170 on a system you already have because it comes in a different color.
And last time I checked, taking computer science classes has no bearing on whether or not you know anything about programming DRM on a proprietary video game platform.