Every creature ever born has its defenses. Tigers have their stripes and sharp teeth and claws. Lions have their manes and also teeth and claws. Birds can fly away or peck at enemies. Bees can sting. Even trees can produce toxins to repel or harm enemies. And humans are no different. Our defenses, however, are more of a social nature. In premitive times staying close to a group of people meant your survival. Socializing was an intricate part of everyday life and even today when it is not necessary for our survival, that intricate balance is still hard-wired into our genes.
In primitive times, being different meant death. If you stood out from the crowd chances were that some predator could more easily pick you off. So societies started to shun people who were different from the cultural norm, to ostracize them because they were dangerous to have around or were undesirable in various ways. That too is still hard-wired into human genetics.
Multiples, by our very natures are different from cultural norms in most places. We experience ourselves as more than one person sharing a body. We may refer to ourselves differently than "normal" people do. We might act drastically different from day to day. And for this we are generally ostracized from society.
So from a very early age most multiple systems learn to camouflage their actions, their vocal mannerisms, their preferences for food, clothes, and a number of other things. They stop referring to themselves by their own names or insisting that others call them by their names. They might even try to force themselves to stop being multiple altogether.
But being multiple usually does not go away. Instead, what happens is a very strong set of ingrained defense mechanisms is created to protect the system, a set of defense mechanisms that learns from the experiences the system has dealt with in the body. For example, a system who have been told to stop talking to themselves will most likely not speak aloud to each other and a system who have been told that their handwriting changes radically and they should settle on one handwriting may develop a "filter" of sorts to filter the handwriting so it looks "normal" and unsuspicious.
Sometimes there is a system member in charge of controlling these defenses. But other times, as is the case with our system, there is no such person whose designated job it is to control them. These ingrained defenses instead rest rather like a thin mask over the present fronter, filtering their actions to make them fit into the norm of singlet society. System members can fight them, and can temporarily over-ride them at times. But they are never truly gone, no matter what you do. They are always there, always dictating your actions.
And why would anyone want to get rid of them? After all they help a multiple appear more normal. They provide that all-important consistency that every multiple needs to pass in society.
But filters can also be harmful. What happens when the multiple in question is around friends or people who know of their multiplicity? The defense mechanisms are still there. And there is no on-off switch. No matter how much the multiple would like to let down the defenses so that personal differences could be seen and the strain of trying to act singlet could be lessened, they cannot. They are trapped behind a mask as it were. It is a case of defenses outliving their usefulness, much like what would happen if an African tiger were to be relocated to Alaska.
Also, sometimes these defense mechanisms filter out harmless things such as a person's individual writing style. For example a person who uses the word "y'all" might be filtered to only use the words "You all." This is, of course proper grammar. But some people have a preference for "y'all" over "you all" and no singlet would be asked to forego their preference of words around friends, as long as the words are not offensive. The defense mechanisms of plurals sometimes demand that they do this, as well as to eat foods they do not necessarily like, talk about things which do not interest them etc. All in the name of fitting in. And truly that seems rather sad to me.