^^ what he said and also you have to level-up the skill lines by using them just like any other skill line.
And yes, they do have benefits - not a massively OP as they once were but still nice.
An old rule of thumb used to be that WW was for stamina builds and Vamp for magicka but latley I've seen some end-game stamina builds (I think Alcast does this) that uses vamp for the passives.