The thinking behind the movie Bounce, Baby, Bounce went something like this:
1.Guys like to watch big, natural tits bounce.
2.Tits bounce more when the girl is bouncing on top of a hard cock.
3.Let's make a movie in which girls are doing this.
This scene opens with Sabina Leigh playing basketball. That makes her tits bounce. Which bounce more, the ball or Sabina's tits? She takes off her top. The guy is totally distracted. Sabina's tits are bouncing all over the place despite the fact that she's wearing a bra. Her guy can't take this anymore. Enough basketball! He grabs her tits and they start fucking, which is fine by Sabina.