Why add in the eggs last when making chocolate chip cookies?
In home recipes the eggs are added whole. They can't be added until after the creaming step or else they will dissolve some of the sugar. They are added before the flour to make sure that the yolks and whites are completely blended.

In this video- the process has been simplified for industrial quantities.

In the step that can't be skipped, the fat and sugar are creamed. All the other ingredients are then added at once and mixed. You can see that the eggs have already been blended with the vanilla so no extra mixing is needed for them.