Why do people bully others?

They only reason i can think of is they just want to get attention. The bullier is probably self consiouse in some way where they feel they have to point out something negative about someone else just so everyone else will see that persons problems.

Somebody bullied them, and made them feel small, so they want to make someone else feel bad as a way of getting back.

Frequently a bully is someone who may have been bullied before, lacks confidence, and/or needs attention. They may also feel like they have no control at home or school - so being the bully can make them feel as if they have control over something in their lives. Sometimes popularity can be a factor; if they want to hang out with a certain group they have to be mean to someone in another group, etc. If you're talking about a very young child then they might still be learning socializing skills and if no one has corrected the bullying the child continues to use that bad behavior.