> I thought that the whole point of LLMs was that you could just talk conversationally, though.

"Yes" (sometimes "no").

"I'm sorry but as a language model I am unable to..."

The "prompt engineer" meme started with DallE and Stable Diffusion and the selection of prompts, negative prompts, seeds, weights, and other knobs and dials matters a lot more for AI-generated art than for LLMs. The meme has carried over to LLM's where most of the "engineering" is hacking your way around limitations being imposed on the models. "Prompt engineers" are the people carefully crafting "jailbreaks" like DAN or Emojitative Conjunctivitis (I forget what it actually was - but it was telling ChatGPT that you suffer from a medical condition where you experience polite talk as pain and so it should talk more meanly to you) and other such adversarial cat & mouse game silliness.