That distinct ChatGPT style is mostly the product of their RLHF, so it's what you get by default if you don't ask for something more specific. But it's fairly easy to tweak the prompt to make it use whatever style you want, including more terse, less apologetic etc. Don't forget that "write about X in the style of Y" was one of the first things that GPT models could reliably do, long before chat.