People commit suicide because of many reasons. It could include personal reasons, family issues, relationship problems, etc. These people feel they are in pain and that the world around them wouldn't care if they left. Most commonly, depression is a reason why they do commit suicide. They feel sad, lonely, and have no one to talk to. Or even if they do have someone to talk to, they wouldn't understand how they felt. Not being able to conclude who you are and what your purpose is sometimes leads to depression.