People like to body shame each other for a variety of reasons, whether in person or on social media:
The culture often promotes unrealistic body types, leading to individuals conforming to these standards and facing criticism.
Individuals who are unhappy with their bodies may resort to self-criticism, which is a dangerous coping method that can harm everyone involved.
Body shame is often used to encourage change, but in some cases, it's often harmful and leads to more harm than good.
Some individuals may not have learned moral values and ethics, which leads them to body shaming and bullying others.