Because they don't appear in any other Disney media like House of Mouse or Kingdom Hearts. Disney itself keeps it separate from their other products.
Eh, I don't care much about either of those. I don't need Aladdin and Simba and Mickey Mouse to all be on screen together to legitimize each other as Disney.
Well you already have the Fables universe and the Wonderland Gang, so I think any of them would be a solid choice. Personally I’d pick Jafar as the first new addition and make him a Green Arrow rogue.