Being a writer takes a lot of really random skills and a, sometimes, dazzling array of weird trivia. It also makes you wonder about things. You have to get into the mindset not only of your characters, but also of everyone else around them. You have to figure out why certain things exist.
As a perfect example I was just contemplating castles and fortresses in a midieval/fantasy setting; specifically their decor. One of the most classic examples of decorative wall hangings in a castle or fortress setting is the crossed swords, or sword and shield, or axes, or what not. Basically weapons hanging on the wall or suits of armor standing in alcoves. So the question is: why the hell would they put those there? I just figured out the answer. They are the original “Break in Case of Emergency.”
With weapons and armor strategically locate along the passageways and hidden corners of the castle or fortress, potential defenders are never far from a source of arms or armor should the need arise. Anyone in the area who happened to be aware of impending or ongoing attack could run to the nearest wall-hanging and arm themselves. Or, if they had enough time and help, could slide into one of the readily available suits of armor.
Isn’t that incredible?
And I never would have figured it out if I hadn’t been writing a fantasy novel. (Sure, I could probably have just looked it up, but figuring it out for myself is so much more fun.)