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.
One being they can get a guy over who is a good wrestler but a poor talker.
In recent years there have been examples of guys doing great manager jobs in wrestling, as previously mentioned
James Mitchell's role in
TNA, and not
that many years since,
Paul Heyman for
Brock Lesnar and
Armando Estrada for
Umaga, when big monsters speak it often kills them because their voice can never match their look (
Bobby Lashley says hello

)