This sport originates from a middle or high school pastime of boys simply being bored and wanting to play basketball with girls. The lack of a basket caused men to use women's cleavage (note can also be played with an overweight man). It has spread to the public and is a common occurrence when friends chill with females.
"Dude, look at her shirt."
"Nice. Let's play breasketball. One-on-one."