Writing is our mirror. We write to reflect on our true self, to identify what is real and what is just a facade; being truthful and honest and deeply reflective and peeling layer by layer of what being a human is, what the human experience is and so on, because only when you fully understand who you are, will you be able to understand what your problems are and what your solutions might be. It is the underlying desire for (and path to) self-actualization - who are you, what is your purpose, what are your doing, and what you outta be doing. Spreading joy and how to be kind to yourself and to others around you is where I'd say most of that soul-searching takes us.
PS: I don't write fiction at all, only my thoughts and ideas and reflections of reality