They are also saying that they have the right to take from everyone and not give back but that the same does not hold for everyone else who must participate in the social learning experience. I actually doubt that any such person even exists. They either just don't have the time they can commit, are unsure of their technique so they don't want to screw up everyone else, or feel that there are better formal instructors around so they decide that it is better that the best instructor take the formal class. However, these same people are the ones that tend to come in the off hours to help their kohai deal with an upcoming test, or help teach kohai about etiquette, or help teach kohai about dojo responsibilities by providing a good behavioural model in cleaning, donating materials, and working on committees to upgrade the dojo. Aikido learning and teaching do not occur only on the mat but all around it.
Students are students cause they want to be.
If a student is forced to be something they don't want to be, you are asking them to quit. I don't think I know of one sensei who really wants to be the chief instructor. You do it because you have an obligation to your own sempai who helped you along the way. You have a life-long debt to them that can't be repaid directly so you will have to repay it by helping your kohai along the same path as you are taking, clearing the way a bit for them. Therefore, if the students haven't learned that lesson that they owe their sempai to become teachers, either of individuals or of formal classes, then the instructor must insist that the students teach classes.