There was a silly horror movie called Crawl that came out a few years back. It's about killer alligators during a hurricane in Florida.
The least-believable part of this very silly movie was that, at the beginning, the main guy in it left his cell phone upstairs when he went to the dark basement to work on something in the house (pipes? I don't remember), which ended up causing the rest of the movie to happen. Of course he'd have taken it with him, for the flashlight if nothing else (and there are lots of other aspects of a smartphone that are super-handy when doing that kind of work).
Think of all the movie storylines that would just completely fail in the era of ubiquitous mobile phones.
Relatedly (sort of), I'm looking forward the day when they stop making movies whose storyline would be destroyed if the protagonist did the obvious thing and pick up the weapon used by their defeated attacker, so that they have a better defense against the next one.
The least-believable part of this very silly movie was that, at the beginning, the main guy in it left his cell phone upstairs when he went to the dark basement to work on something in the house (pipes? I don't remember), which ended up causing the rest of the movie to happen. Of course he'd have taken it with him, for the flashlight if nothing else (and there are lots of other aspects of a smartphone that are super-handy when doing that kind of work).