Did you realize that makeup is like fashion? It changes a LOT over time, and the makeup people applied 10 years ago is different in a way than it is now.
Grandma never left the house without her ghastly matte orange lipstick, and girls nowadays won't leave the house without contour, lashes and structured brows.
Contour is meant to slim the face, or make it appear more youthful (depending on how it is applied). It can also be used to sharpen the nose.
Also, as far as lashes are concerned, if you are fair skinned redhead or blonde you might have pale almost non existent lashes, so rather than applying mascara every single day (which is what girls used to do), you can apply mascara.