Of those that I know that uses makeup none would use the same makeup all the time. For instance practically none of them use makeup when they sleep or do sports/swimming. For everyday use only light makeup and more makeup at parties. So if it in RL doesn't make any sense to always use the same makeup why would it in the Sims?
What does mermaids and vampires have to do with makeup apart from that they also use it.?
Applying the same eyeliner is very easy just choose the one you want then cycle through the different situations and apply the same. Very fast. On the plus side you can then easily skip the outfits where it doesn't make sense like swimwear.
No need to be sorry about that. You are welcome to use eyeliner in a swimsuit or PJ's if you like to. You don't need to choose makeup if you don't want to you can just accept whatever you were given in CAS. Usually it is not too hideous.
