I've watched with envy as some players run up and down the neck, with their left hand, without even a sideward glance at where they're going.
However; when you're playing for four hours a night and trying to keep track of everything else in the room, you can't be constantly trying to remember chords and words.
The capo is, as one of you already said, a tool and an indispensable one at that.
It allows me to play mainly in Dm, G & C configurations which I find easier on the ears and fingers. Easier on the ears because I can better anticipate the changes.