Humans love recognizable patterns and symmetry. Rhymes sound alike, and when coupled with meter, help make the words “stick” in our memory. We also like artificial things that are easily distinguishable from the chaos and entropy of the natural world. We enjoy our feeble attempts at imposing order.

I have two theories, applying not just to rhyme but to traditional verse forms in general (i.e., formal constraints like rhyme, meter, alliteration, etc.):

1. In prehistory—when all knowledge was transmitted orally—constrained verse acted as a sort of verbal checksum to prevent transmitted knowledge from getting corrupted accidentally. And verse patterns became a mental flag indicating that whatever was being sung or recited was important knowledge worth the extra effort of casting into verse.

2. It’s been discovered in many different contexts that humans are attracted to information with novelty to predictability ratio of about 20–25%: if it’s much less than that we get bored, and if it’s much more than that we get lost and/or consider it gibberish. So adding a predictable element like a regular rhyme pattern gives the creator freedom to add more novel elements without losing the audience.

I like the novelty/predictability ratio idea. There is also the idea of “create expectations and satisfy them”, which leads to a sense of stability. Our cultures and genres create expectations. Rhymes tied to a certain metric can become part of these expectations. Of course, you can also create expectations and frustrate them, which leads to a sense of instability. Searching for “fakeout rhyme” videos makes this evident. Pat Pattison, an expert in songwriting, could be a good source on this ☺️