Bicycles as Advertising Props

I'm sure you've seen them, advertisments with models, usually female, astride or leaning against bicycles. In the ones I've seen (and I don't watch TV or read magazines), the advertisers are promoting clothes, and sewing patterns.

Yesterday, while at the Children's Hospital Booksale, I saw this one in an adjacent shoe store.

I wonder if all this bicycle porn increase ridership, sell more bicycles, or do people simply not see them because the bikes they are simply very pretty props?