To wax pedantic.

Starting with the last. Read a play called "We Bombed In New Haven" by Joseph Heller. It's all about smashing the fourth wall.

You might want to look up thse books. David Gerrard's The making of Star Trek, and The Making of 2001 by Stephanie Schwam. Both deal with the problems of creating a science fiction movie at a time when every special effect had to be 'practical' and handmade. For example, on Star Trek there was a scene that involved a salt shaker. Production brought a dozen exotic looking shakers, only for them to decide that those things looked too weird and that the audience wouldn't understand what they were. In the end they used a salt shaker from the NBC commissary and gave the others to Dr. McCoy to use in sickbay.

Also, think on this. To 1960s audiences Uhura as Communications Officer was a big deal. The audiences had grown up with [or actually lived through] WW2 stories where the radio operator was a vital member of the team. With improved communications tech, the people who made The Next Generation decided that the bridge no longer needed a dedicated Communicatuions Officer.

Finally, I can name a dozen stories where a Faster Than Light traveler gets a paper letter or a telegram.