It's not a reasonable question at all. My first reaction was: "maybe the authors did it as a toy project". If nobody is paying them to do a professional and bit-perfect GameBoy emulator then there should be no expectations that the software is going to be good.

That's an insightful reply, and an important point to consider. There's been a number of great answers in this thread, and the general consensus seems to be "the language is a great fit, but the projects haven't had time to mature."

These seem (to me) like reasonable responses to a reasonable question.