I think when you get used to your make-up improved version of yourself if becomes hard to see yourself without it. I know a lot of girls who arent as great with application can go without it but a perfectly applied face of make-up makes eeeeeverybody look better.
I do go out without make-up depending on how long I'll be out for and Im feeling but I usually prefer to wear it because a) I look better and am thus more confident and b) I like to practice!! If I'm just running some errands, I'll go out barefaced and if Im under the wheather I never wear make-up but usually, to meet up with friends or go out for long periods, I always wear my make-up.
We don't need to justify our addiction! Feeling good about yourself is important and I say that whatever can help you relax in your own skin is worth it. Besides, we decorate our houses, our notebooks, our offices, our online profiles... why not decorate ourselves? Of course, if were going to be stuck in the same skin everyday we'll get tired of it- make-up is an easy and removable way to customize ourselves. What's the problem with that?