I will admit that I am slightly metaphysically and spiritually biased on this and this may be a bit pretentious but...
in the question-why should I paint?
who is the one asking the question?,if your "I" is just a concept inside your mind which is also just another thought
how can you derive any essence or drive from a thought that pops up and then disappears.
I guess what I am trying to say is that deriving meaning ,inspiration and drive from thoughts can only get you so far and
at a certain point you have to track back and see what was the actual feeling(which is not conceptual) that got you excited about art(and life) in the first place.
and sorry again for this grasshopper shit maybe it will help someone else because whatever you are doing seems to be working from looking at your art.