I think Craig is right.

for example if some room is design to accomodate two persons, and for instance we have 3 persons, we might think to accomodate the 3rd person in the same room.

But what about if we have more than 10 persons??
Can we think to accomodate all 10 persons to accomodate in same room which can actually accomodate 2 persons?

Here we need external (RAM) room to accomodate them.

Sometimes we need to address large external RAM, maybe for prototyping exercise for some developing project. We might reduce the code at later stage, but while prototyping we can not really maintain the size of code as we wish.

Rauf