Boys are generally unwilling to commit. They flirt around with many girls. While girls want to settle down with one person, they are reluctant to do so. Most commonly, this fear of commitment is because of a fear of loyalty. Many guys find it hard to believe that their girl will be loyal to them.
Others simply think they are too young and have a fear of growing up too fast. They feel that committing to someone will take the fun out of life. Hence, they prefer to roam free. Moreover, this fear of commitment can also be because of peer pressure.