- C takes a lot more context than a high-level language

- a lot of C code out there is not safe, so the LLM outputs that

- C encodes way less of the programmer's intention, and way more implementation details. So unless the author is extremely good at naming, encapsulating and commenting, the LLM just has less to work with. Not every C code is Sqlite/redis/ffmeg quality.

- the feedback loop is slower, so the LLM has less chance to brute force a decent answer

- there is no npm/pypi equivalent for C on which to train the LLM so the pool for training is less diverse

- the training pool is vastly Linux-oriented, with the linux kernel and distro system libs being very prominent in the training data because C programs on Windows are often proprietary. But most vibe coders are not on Linux, nor into system programming.

Sure, you can vibe code in C. Antirez famously states he gets superb ROI out of it.

But it's likely you'll get even better results with other languages.