...I often say that I just think it's fun to wear sometimes. I ddn't want to mae it an appearance-based thing...but I DO tell DD that our culture wants girls and women to feel like they need makeup in order to look pretty -- and isn't that stupid to think that you need lipstick/eyeliner/etc. to look pretty? I tell her that the more women feel like they HAVE to wear makeup, the more they'll buy, and the more money companies will make, and that it's important not to be brainwashed into that trap.
Wear it if it's fun for you and you like it, in other words. I'll also say, I don't have time to put mascara/gloss/whatever on -- just too busy to bother! And when DD asks why I don't wear nailpolish, I tell her that I'm just too busy typing and painting and that the polish will just chip, so why bother? I tell her I have too much to do with my hands and can't be constrained by lacquer.
Speaking of which...I also tell DD that there is lead in many lipsticks, and chemicals in nail polish and remover. She asks, "Don't companies care that this hurts people?" I tell her the truth: no, they don't -- they just want to market their product and make money, and if that means using cheap, harmful ingredients, that's what they'll do - so we have to be smart consumers and inform ourselves about ingredients, quality, etc.