Sorbate is essential to prevent back-sweetened (wines that have sugar or a sweetened flavor-pack added after fermentation) wines from re-starting fermentation in the bottle. If I am making a dry red or white wine (e.g., Cab Sauv. or Chardonnay), I never use sorbate, because of the potential for a bubble-gum-my type flavor/aftertaste. I have personally never tasted it, but have read about it enough to avoid it because the sorbate is unnecessary for 95% of my wines (almost all dry reds). I also prefer to add as few things to my wine that are not grapes or yeast as possible (a little potassium metabisulfite is critically necessary as preservative, but I tend to add less than the usual recommendations).
But if you are making one of the Summer Breezin' or Island Mist kits, they come with the sweetened flavor pack, and failing to add the sorbate would lead to fizzy wine or spontaneously popping corks. The flavoring and sweetness would cover any bubble-gum flavor the sorbate might lend.