Some bullies simply weren’t raised very well and just don’t know any better, so they do what is easy and fun and gets a rise out of people (whether the rise is positive or negative).
Some bullies know that what they are doing is wrong and hurtful to other people, but they’re so selfish, that they just don’t care.
Some bullies are people that have been bullied themselves, and are the type of people that are “followers” and they think that the only way to fit it, or to not get bullied again, is to bully other people first.
Some bullies are attracted to the fact that it makes them look powerful or badass. Most people don’t want to be perceived as weak, and for some people, acting like a bully pretty much assures that they will not be seen as week. They don’t care if in addition to appearing powerful, they also appear as mean.
Some bullies have mental problems or personality problems that make them mean. Some of these types of people can’t help it that they are mean, and some of them may not even be truly aware that they are being mean, because they’re not smart enough or mentally cognizant enough to realize it.
Dealing with bullies is hard because some punishments and/or deterrents work for some types of bullies and don’t work for other types of bullies.
There are all sorts of lawsuits that can be brought against schools if they treat one child, incorrectly, so the schools are hesitant to do anything to stop the bullies, except for to give weak lip service to have no tolerance for bullying.
Some schools (teachers and administrators) really have no idea what to do about bullying, because they have been given absolutely no training. Others have a huge fear of being dragged into a lawsuit for doing the wrong thing.
Most teachers cannot act as parents or babysitters although they are often called upon to do so. They are limited by what they can say and do, legally, and many times parents and administrators have not shown any interest or knowlege on how to effectively handle bullying and how to teach children to resist becoming bullies, or how to report cases of bullying without becoming bullied or ostracized themselves.
In our society, tough people are still seen as super-cool. So gangsta rock dudes, gun-toting former California governors in movies, football and boxing and violent video games are part of the norm, and kids see those activities and try to emulate those behaviors. Being macho is seen as something positive. Learning manners and compassion is seen as wimpy and old fashioned. Until some of these ideals of manhood and ideals about being tough change, nothing is likely to stop bullying.
And because it’s extremely easy for people to anonymously bully other people online, there is really no fear and no public shame to stop people from bullying. My guess it that bullying is likely to get a lot worse in the years to come.