Kathy giving her ring to Johnny

What was the significance of Kathy giving her ring to Johnny? I know she said to remind him of the difference of her and Monique. He responded he knows the difference between her and anybody.

But did ring giving had any cultural or pop significance back then? Late 80s early 90s?

BTW, I don't care what any body else thinks but I love this movie. I watched it again for the 2nd time today (first was last night hahah). The more I view it, the better it becomes. I don't see it as ridiculous at all. Except maybe for the elderly couple mechanic, especially when they started breakdancing! I think the movie is utterly sincere and very heartfelt.