Sex sells, especially if you're selling your product to heterosexual men.
According to a 2008 Belgian study published in the Journal of Consumer Research, the mere sight of a bikini or lingerie model can take a serious toll on male willpower. They discovered that heterosexual men who watched sexy videos or handled lingerie sought immediate gratification - even when they were making decisions about money, soda, and candy.
In this, nude or semi-nude imagery causes a shift in time preference, forcing the male gazer to live in the moment without concern for past plans or future promises. He is powerless to resist. Is it any wonder our world is so ticker-taped with idealized models shilling products at us?