The speed of computing a path from vertex to vertex is faster than trying to generate a point at X distance for the pathing object. So you give the NPC a speed

The speed of computing a path from vertex to vertex is faster than trying to generate a point at X distance for the pathing object. So you give the NPC a speed, and it moves as far along the edges between vertexes in each time interval. The navmesh also helps keep the AI traveling in places that have been marked as safe for travel, without collision or drops.