People like the nostalgia and it gives writers a lot of easy ways out of writing around the internet, cell phones, and other modern technology and lots of stuff for props and sets are junk and can be found for dirt cheap or free.
Also if there's kids in the show, they sure as hell don't play outside after the 80s.
The 90's was basically internet-free, too.
The 80s are connected to the 20s
I think modern pop culture started in the 80s, when you're out of ideas and all your old Hollywood and MTV stars have gone into hiding or dead, when postmodernism has killed all semblance of meaning, just bring it back to the good old days. But not too old, because who the hell is gonna relate to the 50s? Not to mention that decade is canceled because it's sexist. With the exception of classic rock radio which goes back to the 70s and oldies stations that play in retirement homes I've noticed nobody really cares except when it's reflecting the trashy manchild consumerism that took off in the 80s