A method might return, say, some URIs. These might be represented as URI objects or strings, depending on your preference (in some tighter areas of the code we might use String objects, because URIs can be expensive-ish to create, and we might know for sure that the strings in question are valid). If I have a method called getURIs, does it return URIs or Strings? Should the method be called getURIsAsStrings? Perhaps, but it makes for some pretty awkward (and long) method names.

Even if you do have a sensible naming scheme that makes the return type clear, it's rather beside the point. If I have a choice between relying on coding convention or generics, I know what option I'm going to pick.