To say Vader will not use his light up sword is the equivalent of saying he will not see battle. Which may be the case.
But, to spend a moment with my thoughts... I'd like to think a Sith, like samurai, look at their swordsmanship as an art, it is part of their preferred way to battle. If they are going to see action / run through troops they will likely draw their blade. Sure they can use the force or blasters etc, but there is a reason they carry these "ancient weapons", there is something special about cutting a person down. To be a warrior. The intimacy. The honor in battle. And it sets a level and fair playing field for those who step in your path to challenge, otherwise there would be no honor in just choking everyone out. It's a statement in a sense, giving you a chance to battle them and each victory feeding them a sense of greater power. To be unmatched, only until another swordsmen of equal strength and ability can meet your challenge. It is this that makes them who they are. If we are to take this away from them, then the jedi just become silly dudes in bathrobes, with or without glowsticks. Keeping the Samurai aspect in tact is the only reason why I like the idea of Sith/Jedi.
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In closing... Vader may not see battle, but if he does, he will draw his blade.