It's based on account age. These players have set their liveries in different moments of this game. There is a fourth style missing in your picture (the oldest one, basically the top one with driver helmet).
I have the car in the middle and if I were changing my livery, I would switch to newest one. Personally I never liked how liveries look on the latest model and I will never update my livery.
Btw on track all players are forced to use the latest model so any old style exists only on profile picture.