they do it because of fear. Fear that they will get into trouble and be punished or fear that they will not be likes or shunned by others. Some of us never seem to outgrow those notions and blaming others becomes a part of who we are as adults. Not a very good character trait is it?
you can change this behavior. When something gets broken or plans go awry, don't look at who you can blame. Instead, think to youself that it really doesn't matter whose fault it is. Recognize that this is the situation, now what are we going to do about it in order to move forward.
This is a good thought process no matter what the problem. The objective is to try to work throught the problem, no matter who is at fault, to restore peace and get your life back on track.