Disclaimer: I do not look like Penelope Cruz without makeup. Actually, the only time I even come slightly close to looking as good as Penelope Cruz without makeup is when I wear it. So why have I almost completely stopped doing so?
The initial honest answer, I suppose, is laziness. While I'm militant about arriving places on time, my preparation is always two steps behind where I should be. I love sleeping, and my alarm for work in the morning is constantly being set to snooze. Usually I have my outfits laid out and I shower before bed, thus providing maximum sleep time. But makeup can't be applied the night before, and I'll always choose making a pot of coffee over putting on eyeliner.
I also work in retail, with few breaks to touch up my face during the day. I don't know how it happens, but if I'm wearing makeup it's guaranteed to be smeared and messy two hours into a shift. Contacts play a big role as well, since they sometimes dry out my eyes and cause me to rub them. It's not a good combination when wearing mascara. I often have to walk around with raccoon eyes, which is even less attractive (on me) than going bare-faced.
I don't have any moral problems with makeup. While the beauty industry (obviously) sets unrealistic expectations to sell products, I think that a woman should present herself in whatever way makes her feel the most confident. When going out I'll gladly layer on the eyeliner, lipstick and foundation, with plenty of touch-ups during the night. But with good sleep and hydration, I think my makeup-free face is preferable (and easier) during the day.
Do you wear much makeup? How often do you put it on?