Irrelevant if the game lets you build 923473928473243249392743924 refineries/harvesters around your main field. The only thing expanding does in classic C&C games is give you access to more resources in total, not to increase your income rate
. There are tons of problems with allowing players to dry up a resource field quickly. It limits harassment options. Meanwhile in WC3, SC/SC2, and Generals, the resources in a given area last a long time, offering lots of harassment potential. In C&C 3 for example, the blue field on Tournament Arena could be harvested dry in just a couple of minutes, completely eliminating any sort of long-term harassment potential.