I might've been tempted before to shrug and say that part of Seinfeld's humor is to exaggerate stereotypes, and such exaggeration makes the humor go down more quickly. But now it reminds me of how PR's father Bernays linked market forces with this sort of cultural stagnation:
"The American motion picture is the greatest unconscious carrier of propaganda in the world to-day. It is a great distributor for ideas and opinions.
"The motion picture can standardize the ideas and habits of a nation. Because pictures are made to meet market demands, they reflect, emphasize and even exaggerate broad popular tendencies, rather than stimulate new ideas and opinions. The motion picture avails itself only of ideas and facts which are in vogue. As the newspaper seeks to purvey news, it seeks to purvey entertainment." http://www.pentaside.org/article/propaganda-bernays-1928.html
Tayssir