It has a name. The Rule of Threes. https://en.wikipedia.org/wiki/Rule_of_three_(writing)

“The rule of three is a writing principle which suggests that a trio of entities such as events or characters is more satisfying, effective, or humorous than other numbers, hence also more memorable, because it combines both brevity and rhythm with the smallest amount of information needed to create a pattern.”

It’s how I was taught to write, but I understand that my personal experience can’t be generalized to make sweeping statements.

Do you have data that suggests it’s uncommon in human-authored blog posts and more common in LLM-generated text?