There should be a way to turn on or off dispatch centers. One may choose to play one area and not the other in the same account.
Also when one is expanding into another area and a new dispatch center is created for that area, they may not have all the required units built for the new area yet , like HazMat, MCV, BCs, rescues, water tenders, etc They player can chose to turn off the new area and continue to gain credits with the original area until the new area can be put into service with the required units.