The importance of loneliness, as stated by Gravity, Her
Loneliness isn’t a feeling too compelling to be treated as the main subject of a film. If you have one human isolated from everyone else, it’s impossible to build the cause/consequence dynamic that every cinematic narrative strives on.
Now, consider Gravity and Her's main characters: they spend a good portion of their films all by themselves. One in the outer space, isolated from everyone. The other in a relationship with something that doesn't exist in physical form.
Both have to work through some serious issues: the death of a daughter, one painful break-up. The healing process begins as soon as they are completely isolated from other humans. Ryan Stone is trying to get back to Earth, Theodore Twombly is engaging in a serious, sex-filled, full of love relationship with the void (if you “mute” all of Samantha’s lines, Her becomes some sort of quirky schizophrenic dream).
On the course of their “me time”, they become increasingly aware of their traumas and how they’re the ones to blame for their unwillingness to move on from past, damaging experiences.
But it’s almost impossible to create compelling fiction with just one isolated character in a realistic setting, blabbering to no one about his or her problems (literature is the best means to this particular end). To make loneliness look cinematically compelling, Alfonso Cuarón and Spike Jonze had to built their films on sci-fi grounds.
Gravity needs to be visually astonishing, so the audience engage with the story of a woman talking to herself about her dead child. Her needs to disguise itself as a futuristic, digital romance, because this is more easily relatable than the story of a resentful man regretting his selfish behavior in a previous relationship.
Samantha and the space are mere MacGuffins in the great scheme of things. In the sci-fi genre, when you remove the elements that make them sci-fi, what is left is usually a skeleton of feelings tricky to tackle through a realistic setting. Take away the floating from spaceship to spaceship and the software stuff and what you get is a woman finally overcoming the death of her child and a man acknowledging and working on his flaws, all because they spent some necessary time alone.
Alfonso Cuarón and Spike Jonze created in these films marvelous contributions to the Michelangelo Antonioni’s School For Wandering Around With Your Own Thoughts Against Gorgeous Backdrops. And the risk of praising the benefits of loneliness, such an unpopular feeling, paid off tremendously.