Otherwise, it is just another way humans choose to dress their external appearance for their own pleasure, fulfilment and social intentions. It's not as if it's hard to tell when someone is wearing makeup - that is, at least when you're close enough to be able to inspect their imperfections at all.
It seems to me that this idea about makeup being 'fake' stems from heteronormative dating, where a man may feel he is unable to properly assess a woman's beauty (and her attractiveness to him) if her face has been changed in arbitrary ways. But personally, I don't think we should optimize all human encounters for dating efficiency. More broadly, there is no social contract which stipulates you must wield your natural appearance at all times. I think we need not add more social expectations to an already long list.