You may behave in only one way. You must behave in that way in all contexts. You shall use only one name, which we shall call your RealName, all other names being unreal and inferior. You shall have no WalledIdentitys. You shall never change how you behave, and if you try, your new role will never be accepted. Accept our label, and stay in your pigeonhole. PygmalionEffect gone wild.
This is the dark side of SerialIdentity, and it's necessary for society to function.... but TheIndividual finds it oppressive. Those who know WhatIsMultiplicity have the most direct experience of this, but it affects us all.
The expectation of consistent responses to the same social situation is extremely powerful. Inconsistent behavior patterns provoke a fear response. In part this is because inconsistent behavior is a hallmark of mental illness, drug abuse, and personality disorders that fall short of mental illness. But the fear goes beyond that, because of a fear that the inconsistency will break out of the limits of the social contract, resulting in embarassment, violence, or disruption.