Territories are usually drawn once, in a hurry, and then inherited for years. That is why so many operations have a map that no longer describes what actually happens.
Why it matters
Everything downstream inherits the boundary. Density depends on it, because a technician cannot cluster stops that were never his to serve. Capacity depends on it, because a territory holding 40% more recurring work than the next one will produce overtime no amount of optimisation can fix. Customer trust depends on it, because the same face at the door is a territory decision, not a service decision.
How you notice it slipping
Technicians are regularly sent outside their own area to cover. The same neighbourhood appears on three different routes. One technician works late every week while another finishes early. Growth lands unevenly — the territory that was already the fullest keeps getting the new accounts because that is where the sales came from.
What to do
Review territories against recurring workload, not against surface area. Count the hours of committed work inside each boundary, including drive time, and compare it to the hours available. Rebalance on that number. A territory that is 30% over is not a scheduling problem; it is a boundary that has stopped being true.