I've got a lot of knowledge, its helped me get where I want to go. It's helped companies, and my proteges get where they want to go too.
But I still have more and it's accumulating, because I am a naturally curious person.
What can I do with this "useless" knowledge if it just sits in my head?
Offer it to people around me, for free. I didn't exactly pay money for this knowledge, and it's not regurgitating and repeating what's already written (for the most part), this knowledge comes from the intersection and interplay of unique experiences, thought on, and processed through my own unique lens.
Anyone who sits and thinks their thoughts critically, and honestly will have a unique set of "useless" knowledge they have to share with the world. And they should share it. Not because they get something from the world for it in exchange, or that the world has to take it. They get to let that knowledge not be so useless anymore.