Graffiti usually detracts from the thing it is painted on, skin graffiti detracts more since it is injected into a living changing thing rather painted on a building which is by design fixed and unchanging.
Over time graffiti becomes faded, irrelevant, common place and unfashionable to the degree that it was fashionable. In addition to all this skin graffiti also blurs, and the person it is attached to (one hopes) changes and develops from the person they were.
Graffiti can be removed or is more usually painted over simply and quickly. Skin graffiti can rarely be completely removed, and even partial removal incurs cost, causes pain and permanently damages the substance and appearance of the skin, in a way that shows up progressively as the skin ages.
A building may be attractive, but men are programmed to find a woman singularly beautiful, so the contrast between the graffiti and the thing it obscures is heightened, particularly as the woman ages and her sexual beauty fades, leaving her working harder with make up, diet and clothes to maintain it.
A person who thinks ahead would be unlikely to commit themselves to a particular piece of skin graffiti, however significant it might seem now. By contrast, one who had committed themselves is likely to be vociferous in defending it, since the emerging truth is too horrible to contemplate...
Just my two penn'th