Fiction involves world building. Perhaps an author will piggy-back on someone else’s world, a world hypothesized if not conceived elsewhere, or even the current physical world. Perhaps they’ll alter elements here and there keeping the whole recognizable.
But how far do you go? How much do you alter?
Well, it depends. Leaving gaps or utilizing non-chronologically appropriate material might lead to questions about cultural stagnation. Some charges like this have been leveraged against one of the most popular science fiction shows: Star Trek. If you’re curious, check out Cracked’s After Hours video on the matter.
While there may be no need for a plot to discuss books, fashions, musics, and more, these might be background data an author ought to know. The subjective main stream and subculture tropes say a great deal about the current value clashes within society. They describe what’s valuable, accepted and taboo.
Sure, we have T-shirts with Shakespeare quotes, but what’s more common? Modern band and movie merchandise tees or a solid quote from the bard?
Just a rough count, but I haven’t seen a single shirt carrying a logo or graphic today that is more than twenty years old. If the story is sent in modern day or the past, fine. History can be searched. Documents can be parsed through. The future? A bit more problematic.
Pacing will affect the degree to which cultural material is used; however, having a fully fleshed out world serves as a guideline for many other aspects: character motivation, government / legal perspective (especially in thrillers and military novels), interpersonal relationship (cultural biases / prejudices), sudden ‘brain blasts’ (character inspiration or mood change based on external influence), and so on, and so forth.
This can also be important due to copyright issues. Maybe a character speaks only in lyrics or quotes. There’s a fine line which editors and publishers tread between acceptable references and at risk of infringement. It’s especially important in references. If a phrase hasn’t permeated contemporary main stream ideology, it often falls into the latter category or might simply be misunderstood. Having a phrase used which readers can reference back to some in-text cultural nuance adds depth.