I think as a story is meant to be told, if there is nobody for it to be told it loses it purpose. It is no longer a story, it has no worth as a story; it is just a figment of your imagination. Just like magma and lava: you can only call it lava when it is out the earth surface, you can only call it a story if it is out for people to consume.
I cannot believe people who post their story online and goes "I only do it for the fun of myself." No, you certainly do not; if so why the hassle posting it online to an audience to see? You cannot purely write for yourself that way, there must be something intrinsic within you that want to share your story to more people. That is natural wanting to share a thing, that is why you talk and communicate.
For me I also use audience as a measurement of the quality of my own story. I have very little audience so that is mean my story is not likeable or good. It is should not be an absolute value, but it can be insightful. The more opinion the more accurate.
Also if you plan to gain money from your story, you should absolutely and certainly care for audience. Else you would be surprised you get no money.
You might think why utter garbage stories can get successful? Marketing it is. Knowing their audience it is. Even if they are literal dog excretement, but if it is what people see on store front of media they will inevitably consume it anyway