Sorry if this is a dumb question but this is my first foray into the "Pro" side of Mac laptops (currently I have a loyal and trustworthy iBook G4 which has lasted me many years but is now on its last leg, due in part to having yogurt spilled all over it...) and I was just wondering why Apple discontinued the 13" Macbook Pro. I'm seriously looking into upgrading to the Pro version but the 15" model looks so cumbersome, and I travel often with my laptop.