Only for the sake of explaining to the reader the concept of executing from external code memory. And that's the question--is this something that is worthwhile to even go into anymore with so many modern MCUs having on-chip code memory?
I think not. Most chips today with small flash does not even have the pins for external RAM. I think it might be a much better ides to allow either a 40 (such as the Rx2) or a 28 pin (such as a LPC) to be used. In one case you will have enough flash, in the other no means of expanding it.

Erik