"Why"

Why not? they're developing a new technology that will have all sorts of applications. Think of carving out circuit boards at this scale, and so on. That's why.

Why a map? It had to be demonstrated that it was possible to etch things at this scale anyhow, any image would have sufficed at this point. So a map was as good as anything else to demonstrate it was *possible*.

Why not a South Park character? Something was going to get drawn out, and it was likely the whim of the researcher at the time.