That seems like maybe the primary reason.

These days, too, it's easier to write software if you speak and read English.

Just a simple example: Let's say you are using a Javascript function called filter(). It helps a lot to know the base language, because then you don't have to think so hard about remembering its purpose, because the function's nomenclature is a semantic of its purpose.

So if you don't know English, you have to memorize the function name, whereas if your primary language is English, you don't need to to that. It's there in the name.

I complain a lot about AI, but I think AI can help there, eventually.

I'm always really impressed by people who can navigate all the illogical nuances of English as non-speakers (originally). Not sure I could do it!