Because that's not an actual controller. (In fact, you could declare the base controller as an abstract class).
So to avoid confusion with being an actual controller (with the name base), the naming is different.
I'm not sure, perhaps Laravel has some kind of 'fixed' BaseController implementation?
In Phalcon, how you implement this (and a lot of other things), is less strict / not tied to conventions so much I reckon.
Except for the class-naming, I believe this his little to do with PSR standards?