The most common use of this rule that I have seen is for the secondary side of the POCO transformer when one transformer feeds more than one building. In some locations it is the EC's responsibility to install the secondary wiring thru the meter socket to the main disconnecting means of that service. Other locations require us to bury the conduit(s) for the underground service, the thePOCO installs the wire and terminates both ends.
Since the POCO in not under the NEC wire sizes are often different than what an EC would have to run.
My best guess is that the code panel did not want to get into an discussion with the POCOs and the NESC people.
