Using different roles in a plugged classroom is important to manage collaboration. By having students switch between the driver and the passenger, it gives them a chance to see something done and then they get a chance to perform the action as well the next time around. The driver role is more like a teacher role where the passenger is more like a learner role.
This is a good model for pairs of students because if one student feels like they understand a concept more than the other they can help the other student and then the next time around if they are struggling, the other student can take over and help.
Students can bounce off ideas quickly and get instant feedback from one another so they can move forward in the class and lesson.