Mayor is a unique role. Only one per game. Anyone claiming Mayor with no counter-claim or counter-reveal semi-confirms them as being town. That is far more important then extra votes. Using the reveal button too soon will get in the way. Those extra votes will be more likely to destroy Town then help Town if you reveal straight away. You need to gather reads. Can't do that effectively if the Mayor has 3 votes.
So to all you vigs out there, please. Stop (deliberately) killing the Mayor N2 for claiming Mayor without a reveal if that's your only reason to kill them. It's far more likely you'll kill two townies in the process then a non-townie due to Mayor being a unique role. Especially when they were never asked to use the reveal button and weren't the lynch candidate. Anyone claimed as Mayor will always resolve itself through PoE (process of elimination) without the need for a vig. If they claimed Mayor without revealing it's so they can get a doctor on them. Can't be healed once revealed. It'd be suicide to use the official reveal any earlier then necessary due to how easy BG's can be eliminated and abysmal play for a vig to shoot a Mayor claim that hasn't been countered or resolved through day play.