A manager is for the wrestler who cannot talk.
That's not always the case though. Sure, a team like MX goes NOWHERE without Cornette, there are cases like with JJ Dillon where he managed a stable consisting of 4 experts on the mic.
Managers provide several dimensions to wrestling, none of which are needed in this current era. Scott's request of manager divas is proof of this. A woman shaking her ass isn't a manager.