I write because I know I need a creative outlet to stay mentally healthy. Writing is just one of my creative activities. I also write and make music and occasionally, comics.
I think most “creative people” are going to create regardless of whether they get paid or not. But I do strongly believe that good creative work has value and should be paid for. Unfortunately, it is getting harder and harder to earn a decent income in creative fields. But that is a whole other article.
And of course, an audience for your creative output is always welcome, and very helpful.
For me, there is no single answer. It is a combination of “I want to, I need to, I want others to enjoy it, and I would love to get paid for doing it, if possible.”