That would probably have been clearer to newbies, but they already had a complete terminology ready to go from category theory and it's not hard to remember "Functor ~ Mappable". Plus, "obvious" names break down once you start building up hierarchies of these properties. One of the reasons people have a hard time communicating the (simple) ideas behind other algebraic objects like Applicatives, Monads, etc. is because it's hard to come up with short, self-descriptive names for them. The search for such names has resulted in several famously bad analogies, such as "a Monad is like a Burrito".