LLM's are better at software for several reasons:

- lots of high quality training data

- automatic verfication/scoring is straightforward

- AI companies are software companies so are better at tuning LLM's for software

- the goal is AGI, where AGI means the AI can improve itself autonomously. Which requires them to be good at software

While LLM's are uniquely good at software today, they'll get better at other fields slowly as attention goes towards training in those fields.