There’s cool uses for it. Lucas in the BaseMesh Course uses it to mask away the part of his characters he doesn’t want intersecting with the clothes. Those parts aren’t going to be seen anyways and them being opaque would only cause trouble, so he masks them and it works perfectly. Here’s the course if you haven’t seen it:
https://cgcookie.com/courses/basemesh-create-stylized-characters-quickly-with-blender
