The LLMs have been trained on all kinds of code. They often choose a hacky solution because that's what they encountered in similar situations in their training. It generally only takes a few words to guide them to a better design than what they saw in the wild, but if you don't guide them, they follow the herd.

It generally only takes a few words to guide them to a better design than what they saw in the wild, but if you don't guide them, they follow the herd.

That certainly can be true but I would challenge "generally". If you're working on something novel then it's not exactly unusual for even SOTA models to produce a first attempt that makes some very bad assumptions but then get stuck when instructed to use correct axioms instead. This looks a lot like the suduko meme - without any real insight into the problem the models end up just iterating around in circles and never finding a solution.

You probably won't see this very often if you're working on simple CRUD web application where there are millions if not billions of lines of code in the training data set. IME you will probably see it quite frequently if you're working on - for example - software to control some kind of equipment or analyse the results of some kind of experiment where the LLM might have little if any training data about the field you're operating in.