I figured it was for people who hadn't bothered to buy a DS, and wanted to give them a reason to. And for idiots who already had the DS and wanted a new one because it was a gram lighter.
Actually, it'd be more idiotic thinking that you could ever be satisfied with the original DS again after using a Lite. That thing is a fugly, chunky, heavy piece of work, and I haven't doubted my purchase of a DS Lite for a second
Anyways, I was given my original DS as an X-Mas present the year they were released, and while the idea of future Pokemon games on it was great, it wasn't my sole reason for wanting one. That thing is the best thing to happen to gaming in ages, and Pokemon just makes it that much better.