Closest on the map isn't closest on the road
A driver 800 metres away on the other side of a divided road or a one-way street can take longer to arrive than one two kilometres away on the same street. Dispatch that ranks drivers by straight-line distance keeps sending the wrong car, and the rider keeps waiting.
The Matrix API takes every candidate driver and the rider, and returns the driving time and distance for each pair in a single request. Rank by the time the rider will actually wait, and send the driver at the top.
A fare the rider can trust
Quoting before the trip means knowing the trip before it starts. Directions returns the distance and duration of the route the driver will take, so your pricing works from real numbers instead of an estimate, and the same route goes straight to the driver's navigation.
Pickups people can describe
Few riders in Addis Ababa give a street address. They say "in front of Edna Mall" or "near Meskel Square". Geocoding searches places by the names people use and returns coordinates, so the pickup pin lands where the rider means.