Purpose, my purpose, should be independent of the medium or tool that is used to achieve it.
If I take photos of blue whales when they swim at the bottom of the ocean because they start to glow and I want the world to know about this strange phenomenon, I have purpose. The camera is the tool, and the photos the medium, but I could write a story, or tell a story, or draw a picture, paint and painting, etc. My purpose is still the same, and therefore exists. My purpose can’t be , “To take photos”. Otherwise, without the tool, there is no purpose.
What’s my purpose? Do I have one? I don’t know. I think this definition will help me define it. I love doing time lapse, and astrophotography, HDR landscapes. I know that it’s because those things you can’t see without the camera. Is my purpose to show the world things they can’t normally see? Maybe. I feel it has to be something more though.
Secretly (questioning this due to it being published on the internet), my purpose is to just be able to take pictures for a living, but that’s too broad. Sure, everyone wants to do that.
Truly, this is just a jumping off point. Find purpose, keep it independent of tools and medium. Go.