I've actually never worn make-up, which a lot more people judge me for (when they find out - they never guess on their own!) than you'd think.
I have a lot of skin allergies - I know that finding make-up that's OK for me to wear would require a lot of trial and error, and I honestly have never cared enough to make it worth the pain. (And it is pain.)
Apart from that, I've always hated that women are expected to wear make-up - men aren't, y'know?