They do it because of fear. Fear that they will get into trouble and be punisEd or fear that they will not be liked or shunned by other. Some of us never seem to outgrow those notions and blaming others becomes a part of who we are as adulta.d. Not a very good character trait is it ?
You can change this behaviour. When something gets broken or plans go awry, don't look at who you can blame. Instead, think to yourself 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 through the problem, no matter who is at fault, to restore peace and get your life back on track.
Blaming generally does more harm than good not only to the person you are pointing the finger at, bit also to yourself. It hinders forgiveness and gives you a victim mentality. Instead, take responsibility if you are at fault. If you aren't, but are still caught up in the situation, such as a work problem or it has children involved, then just take control of the circumstance, help others work through the problem and get on with life.