Basically translation is harder than you will first think. Here some points and examples.

In tech, localization means making sure the words and concepts in the language the content was originally written in make sense to the person who will be reading in the language you wish to update it to. Localized content requires you to be both linguistically and, importantly, culturally fluent with the community you’re trying to serve.

Still english is the implicit default.

They got a point here:

Shared devices are a thing: the “device language preferences may not be the person’s written language preferences” fact