In the old days when these offices were built we were providing copper services to customers. Copper had a maximum transmission distance of 3 miles. That meant we needed a CO or CEV somewhere within 3 miles of every customer with equipment to service them. This led to them building small COs in rural areas just to service a few hundred customers.
Fiber optics can transmit data around 100 miles without needing a repeater. So the recipe for selling a CO is to migrate everyone onto fiber services coming out of a further CO, then harvest the copper, shut the equipment down and sell it.
Hope this helps