Why some single comb chicken leaf over?

the comb is the crown of the chicken. It's attract some chicken hobbyist. The red blood color make the chicken looks handsome. As the chicken comb grow up they look leaf over especially the single. We rarely find some chicken comb leaf over such as pea, cushion and other. I saw this case happen in rose comb such as silkie chicken. 

The comb is full of blood capiller and gel. The function of comb to keep the chicken body temperature. It is important part of chicken body. Without comb chicken may leave but it is not beautiful as the chicken that has red blood single comb. 

The leaf over could happen as the chicken grow. You may not see the young chicken comb leaf over. The older chicken that age more than two years suffered comb leaf over.. the pension of chicken layer also suffer comb leaf over but it is not visible as the what happen in rosters due the small size of the hen comb. The comb could not cover the chicken hen. 

Some chicken leaf over because the fighting. A roster may break the other roster camb. The kick of the rosters is strong enough to damage the chicken comb. That is why , the game rosters owner do not like single comb game chicken. In my hometown, there is a prcatidce of cutting comb. To me, it is not good. It could torture the chicken. you are better to buy other chicken rather than cut the comb the chicken . I do not whether the cutting of chicken comb is forbidden in overseas.