A fashion started in the Victorian era, where people of means and maybe looking to hook up, but not necessarily interested in marriage, would wear a ring on the little finger of their left hand.
In the centuries since then it was mostly a sign of wealth or membership in a group, especially if it had a signet (a design which in the olden days was used to put one's signature mark on things).
In the 20th century it became a look of the fashionably jet-set.
Today it may just mean you are wealthy or have wealthy friends who gave you a pinky ring as a gift.
Here's an interesting site about pinky rings:
https://www.gentlemansgazette.com/pinky-ring-guide/
Wearing a wedding band instead of a signet type ring on your pinky may mean you have a liking for this small sized ring which only fits on your smallest man sized finger and that's usually your left pinky finger. Why wear a small ring, well, because it was probably made for smaller hands, like dainty female hands or child fingers.