What's the deal with Disney Princesses?

Don't get me wrong, I'm a HUGE Disney fan. But it struck me today walking around the toy section in Target that you rarely see any princesses aside from Jasmine, Cinderella, Belle, Ariel, Snow White, and Aurora in coloring books or dolls. Tiana's only around because she's the newest...but aside from that, you'll rarely see Mulan and Pocahontas. What's the deal? Is it because they're newer than the rest and so they never changed the formats? Or were they just never as popular? I have my speculations...What are yours?