Question

why do people build false images themselves or wear masks

Answer 1

1st reason , to act in TV or or any live show
2nd reason, in robery, to hide there identity.

This is the possible answer think

Answer 2

Every human in this world has a desire to be appreciated by people around them. This tendency is inborn.Some people have it more, and some people have less.
The day from our birth,we encounter with different kinds of people.We find some people so clever or foolish,beautiful or ugly, and being respected or ignored. As we want to be renowned by everyone,we have a tendency to learn and imitate the behaviours and characters of those people getting a respect in the society. (Here, ociety means our school,class,neighbourhood,peer groups etc)
Thus, in the great desire to get the same rewards and respect being given to those people, we forget to be ourselves and live our life imitating many people. These kind of behavioural imitation actually happens unknowingly.
This is a general case.
There are other cases where people make false images of themselves to cheat somebody or get some other benefits.