why can't I grow my hair long?

How is it some people can grow their hair to the floor and others can't grow hair past their shoulders? There are three phases of hair growth. If you genes do not allow your hair to stay on your scalp long enough during these stages it will not get longer. The developing stage where hair is formed is anagen then the hair stops growing in the catagen stage. When the hair remains on your head and is adorning and protecting you is the telogen stage. The hair sheds and falls out in the last stage around a hundred days or so. So if your hair continues to grow longer during the first stage and holds on longer during the last stage you will make it to the floor. If your genetic clock stops growing during the first stage at your shoulders there will your hair adorn you.