Throughout history, women's breasts have been utilized as fashion accessories. Displays of cleavage have always had a fashionable appeal, particularly if they are adorned with jewelry. Fashion designers highlight the breast in many different ways -- now not just cleavage, but side boob and underboob are also used to fashionable advantage.
And occasionally, most delightfully, they just use the entire bosom.
This was on display -- nicely so -- by the currently supremely in-demand Gigi Hadid (who I must note had a great elbow to the face of her hugging prankster, and the guy deserved a broken nose for his effrontery).
But back to Gigi and fashionable breasts - read about it (and get plenty of visual examples) here: