User blog comment:Bluegear93/Custom Shepard/@comment-68.45.190.47-20111105044720/@comment-1900300-20111106075626

Maybe because it is impractical to were makeup in a combat situation as you may not be able to remove it for a long time. And hopeful if it you face is exposed to sudden great heat the make will not exacerbate the injury. Maybe you will be required to get up on short notice, and thus not have time to do this. Maybe having makeup on may worry inferiors since it shows their superior spent a lot of time applying this make up rather then focusing on the mission or working their post. Maybe the long hair would obstruct vision. Maybe the shiny lip-gloss may give away your position in low light situations. Maybe perfume would make it easier to detect you if you are close or to track you. Attractive woman can be as much soldiers as a man, but practically must come before luxury when lives are on the line.

PS John Shepard does not look like a solider that much either. He looks. . . well like a supermodel. But this is justified in-universe due to genetic engineering.