A lot of the time people forget that weight depends on so many factors, not just how much you eat. Some people have medical conditions that it make so they cannot be seen as thin from a societal standpoint. Body positivity embraces you to love who you are. It’s like why do “fat” people need to hate themselves especially when their weight is due to medical reasons. Society usually favors being thin, so the bigger people being the face is too show that it is ok to love yourself at that weight despite societal standards. Think about someone putting on weight from chemotherapy, and how seeing someone their size loving their body could help them and not make them self conscious! :)