Enter Pozzo and Lucky. Pozzo drives Lucky by means of a rope passed round his neck, so that Lucky is the first to enter, followed by the rope which is long enough to let him reach the middle of the stage before Pozzo appears. Lucky carries a heavy bag, a folding stool, a picnic basket and a greatcoat, Pozzo a whip.
POZZO
(off). On! (Crack of whip. Pozzo appears. They cross the stage. Lucky passes before Vladimir and Estragon and exit. Pozzo at the sight of Vladimir and Estragon stops short. The rope tautens. Pozzo jerks at it violently.) Back! (1.290)
From the moment they enter the stage, Pozzo and Lucky fulfill the roles of master and servant.
POZZO
Ah! Why couldn't you say so before? Why he doesn't make himself comfortable? Let's try and get this clear. Has he not the right to? Certainly he has. It follows that he doesn't want to. There's reasoning for you. (1.432)
This is arguably the most explicit statement of classic existentialist reasoning in Waiting for Godot. There is no such thing as slavery or confinement, Pozzo argues here, since every action one performs is a matter of choice. If Lucky doesn’t put the bags down, it is because he chooses not to, not because he isn’t allowed.
POZZO
I do. But instead of driving him away as I might have done, I mean instead of simply kicking him out on his arse, in the goodness of my heart I am bringing him to the fair, where I hope to get a good price for him. The truth is you can't drive such creatures away. The best thing would be to kill them. (1.495)
Pozzo believes he is doing Lucky a service by enslaving him; and, in one sense, he is. This could be the reason that Lucky is considered lucky—someone is around to tell him what to do. Left to his own devices, he may be as helpless and miserable as Vladimir and Estragon.