I read an article in a scholarly journal which espoused he theme that Seinfeld was based on an old Jewish motif, namely, schlemiel, schlamazel. (That's right, same as in Laverne & Shirley). The characters of Jerry, Elaine and George are Schlemiels and Kramer is the Schlamazel (that's the lucky gentile). The writer postulated that the schlemiels were Jewish, as they are in Jewish folklore. So basically it's a Jewish thing except for Kramer. The schlemiel is, if I remember correctly, a striver who always falls short--maybe they try too hard. The schlamazel just putters around and gets lucky. I forget the name of the journal but it was in the Univ of Houston library.
Randy Smith