Why does sex sell?
It turns out that the notion that "sex sells" is a bit of a cultural myth. A 2015 meta-analysis  looked at the impact of sexual content on buying choices in 53 experiments, and concluded that brands advertised with sexual content were remembered less often, evaluated less favourably, and less likely to be purchased than brands non-sexual ones.
The "sex sells" mantra originates from the fact that sexual content is likely to grab a person's attention.1 However, the same meta-analysis  concluded that this very fact is why sexual media is less able to sell a product – people are predisposed to attend to emotionally arousing cues such as sex or violence, which takes cognitive resources away from considering the product on offer.
- For example, the success of an advertising campaign is often based on number of views (since that's relatively easy to measure), but this doesn't always correspond to purchasing behaviour.
-  Lull, Robert B.; Bushman, Brad J. (2015). Do sex and violence sell? A meta-analytic review of the effects of sexual and violent media and ad content on memory, attitudes, and buying intentions. Psychological Bulletin. 141 (5): 1022–1048. doi:10.1037/2Fbul0000018