1) You look at the results of what you've done and say, "Wow! I did that!" (Or alternately, you get a compliment like, "That looks even better than the photograph!")
2) Doodling is proven to help memory. Studies have shown that people who take notes on paper remember better than people who only take digital notes. What surprises many people is that people who doodle also remember more than people who only take digital notes. Muscle memory reinforces brain memory.
3) There are several drawing "recipes" (Zentangles, Neurographica, etc) that are used meditatively and/or as a means of connecting to your subconscious. What they have in common is a simple set of rules that evade ego-blockages by removing the expectation that the result has to look like anything, making the process its own reward and a good-looking picture at the end a bonus.