A radius on a map is not a radius in traffic.
A twenty-kilometre circle drawn around a Sydney business looks reasonable until you drive it. Crossing the harbour at the wrong hour, or moving between the inner west and the northern beaches, can take longer than a trip between suburbs twice the distance apart elsewhere. Radius targeting drawn in kilometres routinely captures enquiries that are commercially unviable once travel time is counted. WIF sets service areas by how far the team will genuinely travel for a job, which is often an irregular shape rather than a circle.