Putting on makeup makes you look pretty temporarily on the outside, but what are you actually putting on your face? The chemicals in the makeup enters your face and may make you look even worse over time. There have been studies conducted, based on the ingredients listed, to see which brands put the most harsh chemicals in their makeup products.
From Good Guide:
I was surprised to see Urban Decay score so low, as they make one of the best eyeshadows in my opinion.
Of course, putting on a primer or a base before actual makeup adds a layer of protection from the makeup, so it is important to not apply directly on the face. I always use moisturizer on the face and lip balm on the lips before any sort of makeup. Moisturizer is a good base as it softens the skin and reduces dry patches and flakiness.
Additionally, using a good primer/ base allows the makeup to apply better and look better overall. For this reason, I use a face primer on days when I am using heavy makeup.
It is better to use less chemicals/ heavy makeup so that your skin naturally looks healthier, rather than pile on a load of makeup and look smoking hot, and then look like a zombie when you remove it.