I started to think about why it was such a common occurrence, and I posited that it was based on the common advice of "write what you know." And what a person knows most intimately is themselves.
My friend brilliantly retorted, "know better things."
I really loved that comment. It made me laugh. But more importantly, it is a great corollary. Not everybody cares about what you know. To grow as a writer, you should task yourself not only with improving your ability to communicate, but also with increasing the range and depth of subjects you can write about.