I think the problem is that design teams don't bake in internationalization when it is not explicitly asked for. It used to be the same thing for responsive pages.
Design tools are also severely lacking here. Even modern tools like Figma have no way to manage copy well (e.g. swap out copy for different "sets" of strings to test the design with variable-length translations). Heck, you can't even use the spell checker or Grammarly on text boxes or comments despite it being a browser-based app.