Why do people brag about who they are
because people think they are better then others and really don't see maybe one day reality with hit them in the face
because they are self centered and think they are the mist important people in the world. But their not so don't be bothered.
Sometimes human instincts overpower us.
"Bragging" is usually done by people who are very insecure. To make up for their lack of self-esteem, braggers try to build themselves up by saying how wonderful they are, when in reality, they don't feel very confident about who they are. :)
Cuz they think their cool like that and they think they'll kill themselves if they don't be theirselves.
Because that's their personality, they can't change it. ;)
Usually due to insecurities and/or low self esteem. Or they have an ego problem, possibly narcissism.