This just made me realize that every time you see a strong AI in fiction, it still has a computer-sounding voice. If we ever develop strong AI, we will probably already have perfectly natural speech synthesis. And if not, the AI could develop it for us.

But I suppose an AI might choose to use a computer-sounding voice to remind us that it is a computer. Kind of like those inaccurate sound effects in movies - they have become so common that it seems more wrong to omit them. (TV Tropes calls this "The Coconut Effect".)