Oh absolutely, the type enhancement is what makes it so interesting to use, but the point is that it's not necessary for it to be a mixin. It's a very nice extra.
I'm not sure about python, but Ruby completely inlines the mixin's code. It needs to do this because instance variables can be created anywhere, including from inside the mixin, but they still need to apply to the object of the actual class. This gives interesting cases for collisions, where 2 mixins create the same instance variable, but it's a decidedly non-inheritance way of doing it.
