It is important to practice minor scales, after all, much of the most interesting music ever written is in minor keys. No, you don't need to do all 3, pick one and live with it. I personally play a hybrid version with a flat 6th and sharp 7th in both directions. I do this because it is difficult to play that augmented 2nd, it is a good stretch for the hand, and helps me get ready for whatever I might encounter that day.