I often have those curious and sometimes doubtful thoughts about why I create these sorts of things. The quickest response I have is how natural it is. I am not designed for many other things. Creating what I create happens just as my lungs keep moving without me telling them to. I have to do it.
One of the biggest motivators I have is taking something that was but an idea in my head, just a neuron politely flaring up when I feel like I should be on some other task, and then turning that formless idea into something I can see, feel, hear etc. Something I can sense tangibly. Holding a comic I wrote still feels great. Seeing others look at them makes me feel like a proud parent.