Why does kennedy repetedly refer to both sides in the middle of the speech?

he refers to both sides to point out the similarities and differences to make his point . This affects other listeners because it makes the argument and or point stronger when comparing and contrasting worlds then and now so we as people can see what’s wrong and what’s right

Explanation:

closer examination, however, finds the mcdonald's kind of job highly uneducational in several ways. far from providing opportunities for entrepreneurship (the lemonade stand) or self- discipline, self-supervision, and self-scheduling (the paper route), most teen jobs these days are highly structured — what social scientists call “highly routinized.”  

true, you still have to have the gumption to get yourself over to the hamburger stand, but once you don the prescribed uniform, your task is spelled out in minute detail.