Advantage of adding costmap_2d::ObstacleLayer plugin to global costmap

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I was going through this Husky Navigation tutorial. This tutorial allows us how to navigate the Husky bot without using a map.

It has 3 yaml files for configuring the costmaps - costmap_global_laser.yaml (for global costmap) , costmap_local.yaml (for local costmap) and costmap_common.yaml (for both global and local costmap).

This is how costmap_local.yaml looks-

global_frame: odom
rolling_window: true

plugins:
  - {name: obstacles_laser,           type: "costmap_2d::ObstacleLayer"}
  - {name: inflation,                        type: "costmap_2d::InflationLayer"}

This is how costmap_global_laser.yaml looks-

global_frame: odom
rolling_window: true
track_unknown_space: true

plugins:
  - {name: obstacles_laser,           type: "costmap_2d::ObstacleLayer"}
  - {name: inflation,                       type: "costmap_2d::InflationLayer"}

Why have we added an costmap_2d:ObstacleLayer to the costmap_global_laser.yaml when it is already included in the costmap_local.yaml? Are there any advantages in terms of path planning?