Keep in mind this is simply an opinion, and it is not meant to hurt anyone's feelings. You asked!
Because the girls who cake it on are more likely to date scumbags.
The scumbags know this.
The girls with the natural look are usually more down to earth and real. Although they have flaws, letting them show is not a big deal because they know the guys who are worth it won't care.
Good guys see through their flaws and know this.
Girls who cake it on aren't bad people, they just tend to be a little more superficial and perfection-oriented. Guys may interpret this as thinking they're "easy" or shallow enough to date/sleep with them.
Natural girls are seen as having more potential for a "serious" realtionship, which not all men are looking for. Therefore they may avoid girls they would get too attached to. Fake females are easier to just see as dinner, a movie, and maybe sex.
That's what most people think, although as with everything, there are exceptions. The guys who only go for the girls who cake it on and dress like hookers are the guys to stay away from. The guy who will date the girl with no makeup in jeans and a tee is the one that knows how to pick 'em :)