The gauntlet button is a very important engineering invention for the full sleeve shirt for the following reasons:
When buttoned, it keeps the tapered forearm in shape along with the cuff, in a slim fit. Had it not been there, the palms would not have gone through in the first place comfortably.
In a loose fitting, or relaxed fit shirt, the gauntlet button prevents the vent from ballooning and gathering behind the cuff, both barrel and French.
The need for a gauntlet...