it's the extra energy that we put into playing while standing.

If that's how it is for you, fine. But it works the other way for a lot of us - less energy wasted on standing means more available for playing. And more accuracy too. And I'd dispute that about "easier to catch eye signals", especially if the musicians are moving around a lot.

Seated can be just as visual as standing. The Chieftains were always a treat to look at.