Pretty much every plot or story twist based on the absence of mobile phones in pre-'80s literature is obsolete. Many movies have scenes or events that simply wouldn't be a problem if the character could pull out a flip-phone, and it's rarely explained in any way... it just is/was, and we all knew it.

For example, the Seinfeld episode "The Chinese Restaurant", which revolves entirely around George waiting for a payphone, leaving a message on someone's answering machine and waiting for them to phone him back on the restaurant's phone.

Meanwhile, with the opening monologue (http://redirect.viglink.com/?format=go&jsonp=vglnk_149567341344612&key=ce270d38103a630c3181db372a25a052&libId=j33pav4a010004p6000DAnax0tv6b&loc=http%3A%2F%2Fboards.straightdope.com%2Fsdmb%2Fshowthread.php%3Ft%3D826692%26page%3D2&v=1&out=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DFCcdr4O-3gE&ref=http%3A%2F%2Fboards.straightdope.com%2Fsdmb%2Fshowthread.php%3Fs%3Dac5f51ec74ba47e4b4f818a2c1024215%26t%3D826692&title=%22Dated%22%20lines%20in%20media%20-%20Page%202%20-%20Straight%20Dope%20Message%20Board&txt=opening%20monologue%20of%20%3Ci%3EThe%20Outer%20Limits%3C%2Fi%3E) of The Outer Limits, most people born after 1980 would probably have no idea that television sets used to have little knobs called "vertical hold" and "horizontal hold" that had to be manually adjusted to properly synchronize the picture.

Kids watching Seinfeld would probably see the black landline phone in Jerry's apartment, and say "What's that?" George's answer machine (again, what's that?) playing his greeting to the theme of Greatest American Hero...huh? Elaine bent because her area code changed (on her landline phone???)?