Pure speculation, but I wonder if it goes something like this: Women who take sexy selfies are sluts, especially if they post those selfies on the internet. Whether they're advertising services or just advertising a one night stand if you buy them dinner, it's all the same with sluts. And especially if they're making a living off their appearance, there's really no difference between a sexy slut who gets money out of the men she "dates" or the slightly-smarter slut who entraps a man in marriage and extracts money from him for the rest of his life. Either way, it's women using their appearance for money, who are willing to provide sex on a trial basis before pursuing a larger commitment.
Unsexy sluts are still sluts, but are less appealing because they aren't obvious status markers the way 9s and 10s are. But the mechanism for obtaining a slut -- whether for an evening or the rest of your life -- is essentially the same. It's just that less awesome dudes have to settle for less sexy sluts.
Now, if you'll excuse me, I need a shower.