The keyboard key is usually a hyphen, not an en-dash.

But I agree that because LLMs are trained on public documents, and most of those are written in Microsoft Word which has auto-format enabled by default, that is probably the source of so many LLMs using them.

Almost nobody, relatively speaking, even knows they exist, let alone goes out of their way to figure out the ALT code combination to use them. Most people can’t get their, they’re, and there right.