In the absence of any other context, that's probably a sensible default behaviour. If someone is just asking "write me some code that does x", they're highly likely to be a beginner and they aren't going to be able to understand or reason about a more sophisticated approach. IME LLMs will very readily move away from that default if you provide even the smallest amount of context; in the case of this article, even by doing literally the dumbest thing that could plausibly work.
I don't mean to cast aspersions, but a lot of criticisms of LLMs are really criticising them for not being psychic. LLMs can only respond to the prompt they're given. If you want highly optimised code but didn't ask for it, how is the LLM supposed to know that's what you wanted?