When teaching kids , why manners are important to be taught ?

Because without it would be delayed too Education

I believe that manners are something more important than learning a subject. As a human being manners are basic thing to retain our position as "the best creature". If we want to educate our children than we have to know that manners are a part of education. 

Just teaching a subject to a child can make him outstanding in that particular subject . It's just like training a pet in certain things but by educating him we build a "human being" with special skills in that particular subject.