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As I've grown older, seinfeld has become funnier than ever, however I feel there are a lot of instances where Seinfeld doesn't seem to understand how the real world works.

George is getting wedding invites a month before the wedding - was boomer weddings like this? Is this a privilege thing? Everyone who is anyone is already invited so they have to do it last minute so certain people don't come.
Gyro prounced JI-ROW - never heard it pronounced that way, especially people from new york
JFK's clubs sold for hundred's of thousands but Peterman was trying to get them for $10,000? The audience laughed

what are some other examples?

There was some in seinfeld's stand up bits too, which I guess is part of the show. He did one about the skydiver wearing a helmet and says if you're chute doesn't open that helmet is wearing you for protection. Like no, when your chute opens you're still hitting the ground pretty fast and can hit your head on things.