I sort of like the fact that fighters work different for the Imperials and the Rebels. Rebel fighters are stronger and have hyperdrives, while the Imperial fighters are free. Gives both sides some unique flavour. Introducing carriers for the Rebels would blur this difference, and that's not a good thing in my mind.
"We think in language; therefore, the quality of our thoughts can only be as good as the quality of our language."
-- George Carlin