Does anyone know why the smurfs put the little black ropes over each and every door of the train that goes between the main terminal and gates 60-99 (where delta is)?

One smurf sits on a chair, the train arrives, he walks along the outside of the train (Extremely slowly) then individually pulls the ropes down one by one (did I mention very slowly), culminating in him finally turning a key to open the doors. This agonizingly slow procedure doesn't happen on the higher gates. I'm guessing it has something to do with international....