Pet peeve: Classic female skins with baked-on make-up
Plain classic female skins are hard to find
If you go around freebie sims that are old enough to still have classic skins, and you're looking for female skins, you'll stumble upon a phenomenon: Almost all of them have firmly baked-on make-up that can't be removed.
Okay, I somehow get it. It's easy for newbies to make a "sexy" avatar without having to hunt down make-up tattoos which are hard to find anyway. It's more convenient anyway for those who always want to wear make-up. And the classic system avatar has only got four tattoo layers, one of which is almost always occupied by a hairbase tattoo, and the skin makers probably wanted to save the other three for actual tattoos.
But it's utterly inconvenient for those who don't want to wear make-up all the time, the same make-up even. If it's hard to find a skin without make-up, it's next to impossible to find a good one without make-up. And as everyone baked their make-up onto their skins back then, hardly anyone made separate make-up.
I had that problem in my early days: I wanted a good skin without make-up which at the same time didn't look like I had silicone boobs or a tanning bed to sleep on at night. It was eventually solved by Jupiter: He built skins without make-up. Lots of them.
I've also found make-up tattoos, both complete make-ups and separate elements such as lipsticks or eyeshades. Also, I don't have to worry about how many layers it takes up: Bakes-on-Mesh offers me theoretically more tattoo layers than the system body has layers altogether. But they would be impossible to use with a skin that already has make-up on it.