Getting Down & Dirty With Mr. Clean
Reading them you'll note that sex doesn't always sell ~ while it may do better in spam clicks, sex has been show (along with violence) not to really lead to sales.
The obvious distinction is that in spam one is using sex to sell sex; that's fair and simple. You're showing the potential customer who is interested in porn, porn. But in the other cases, sex is being used to sell shampoo, cars, beer and anything but sex itself. While you've got their attention, and as the study indicates, got them thinking about sex, you're not selling or delivering sex. Bait & switch doesn't work, least of all here where the product is at least several steps removed from the turn-on.
Likely the ads which posture sex but are unable to deliver it do more to get those porn spam emails open.
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