I only use it if there is residual sugar, or I'm backsweetening. If you have a completely dry wine, there should be no need for it - particularly if your sulfite levels are appropriate.
I only use it on wines that I plan on adding sugar back to. I have used it before in wines which finished kind of sweet to help make sure fermentation would not kick back up.
Not a big fan of sweet wines. All of my wines are dry with the exception of my port (which uses high ABV to kill yeast), so I never need to use sorbate.