Almost all people blame someone else at one time or another for something that has happened in life. It is a part of human nature. On the other hand, some people are mature enough to say that what they did was wrong and are sorry for what they have done. These people, throughout their lives have been taught what is right and wrong and can distinguish if they have been acting a certain way. They then can be responsible to do the right thing.
People often do things and when questioned about it, they blame it on others.
There are a few reasons why people do this. One is so that if they do it just because, it doesn't make them look bad. Another reason is because they pick up on habits of their friends but they do it because their friends made them, instead of just realizing that they do it by themselves. People just don't want to or just don't take responsibility for their own actions. It's not too hard to realize that one can make their own choices and do what they want to instead of always having a reasoning or blame others for their actions.