nta, but I wear makeup because I like to wear formal sort of clothing (pencil skirts, blouses, etc.) and it completes the look I'm after. In the end it probably is shallow nonsense, but I've always liked feeling put together and fancy even just to go to the mall. Sometimes I also just like getting dressed up for the sake of it, not even to go outside at all.
It may seem like a waste of time to you, but the enjoyment is derived from matching different colours and shapes to discover something that you find works as a cohesive whole tailored for your own tastes and body/face. I can't speak for people who strictly follow trends, but for me it's mostly for aesthetic pleasure. I like to create art for the same reason.
I agree anon was getting touchy saying that you're lazy for not wearing makeup, but getting on our backs for wasting time is equally touchy. There is no objective measure for what is the best use of free time. Humans do not exist for any purpose despite what value you have arbitrarily assigned to certain actions and hobbies. You can make goals for yourself, as we all do, but they do not apply to every person on Earth. Within the parameters of the law and other societal functions we get to decide for ourselves what we value most, based on personal principles and benefits gained. I have judgments I can pass on many people since they don't adhere to my moral code, but I know deep down that it's irrelevant.