because the point of a role playing game is to make a character and develop it by roleplaying it in the face of challenges.
origin characters remove all of the agency by having everything pre determined.
hell, did you play Temple of Elemental Evil with the default party or did you make your own?
If you don't want to play origin character, nobody forces you to do so. Just make a character you like and go for it. What's the point of your whining?
