The people of the red tower think that if you get capped you are awesome and cool and stuff but they don't know that when you are capped you must obey the tripods.
The people at the red tower who are capped act like normal people so the uncapped don't know that you are not free.
Since the capped get to be knights or dukes kids unknowingly give up their freedom to become a knight or duke.
These are all opinions of what I think.