husky spawns successfully but spawn_model node not found

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I am running the husky_empty_world.launch file (see below) inside the husky_gazebo package. Inside this launch file is call to spawn_husky.launch file (see below).

I have this piece of code inside the spawn_husky.launch file -

   <node name="spawn_husky_model" pkg="gazebo_ros" type="spawn_model"
            args="-x $(arg x)
                  -y $(arg y)
                  -z $(arg z)
                  -Y $(arg yaw)
                  -unpause
                  -urdf
                  -param robot_description
                  -model $(arg robot_namespace)" />

But when I launch the husky_empty_world.launch file and run rosnode list in the terminal, I only see the following items -

/base_controller_spawner
/ekf_localization
/gazebo
/gazebo_gui
/joy_teleop/joy_node
/joy_teleop/teleop_twist_joy
/robot_state_publisher
/rosout
/twist_marker_server
/twist_mux

There's no node named spawn_model in this list even though a Husky bot is getting spawned in the Gazebo world. Why is this happening?

husky_empty_world.launch

<?xml version="1.0"?>

<launch>

  <arg name="world_name" default="worlds/empty.world"/>

  <arg name="laser_enabled" default="true"/>
  <arg name="realsense_enabled" default="false"/>

  <include file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="world_name" value="$(arg world_name)"/> <!-- world_name is wrt GAZEBO_RESOURCE_PATH environment variable -->
    <arg name="paused" value="false"/>
    <arg name="use_sim_time" value="true"/>
    <arg name="gui" value="true"/>
    <arg name="headless" value="false"/>
    <arg name="debug" value="false"/>
  </include>

  <include file="$(find husky_gazebo)/launch/spawn_husky.launch">
    <arg name="laser_enabled" value="$(arg laser_enabled)"/>
    <arg name="realsense_enabled" value="$(arg realsense_enabled)"/>
  </include>

</launch>

spawn_husky.launch

<?xml version="1.0"?>

<launch>

  <arg name="multimaster" default="false"/>

  <arg name="robot_namespace" default="/"/>

  <arg name="x" default="0.0"/>
  <arg name="y" default="0.0"/>
  <arg name="z" default="0.0"/>
  <arg name="yaw" default="0.0"/>

  <arg name="laser_enabled" default="$(optenv HUSKY_LMS1XX_ENABLED false)"/>
  <arg name="realsense_enabled" default="$(optenv HUSKY_REALSENSE_ENABLED false)"/>
  <arg name="urdf_extras" default="$(optenv HUSKY_URDF_EXTRAS)"/>

  <!-- Optionally disable teleop control -->
  <arg name="joystick" default="true" />

  <group ns="$(arg robot_namespace)">

    <group if="$(arg multimaster)">
      <include file="$(find husky_description)/launch/description.launch" >
        <arg name="robot_namespace" value="$(arg robot_namespace)"/>
        <arg name="laser_enabled" default="$(arg laser_enabled)"/>
        <arg name="realsense_enabled" default="$(arg realsense_enabled)"/>
        <arg name="urdf_extras" default="$(arg urdf_extras)"/>
      </include>

      <include file="$(find multimaster_launch)/launch/multimaster_gazebo_robot.launch">
        <arg name="gazebo_interface" value="$(find husky_control)/config/gazebo_interface.yaml" />
        <arg name="robot_namespace" value="$(arg robot_namespace)"/>
      </include>

      <!-- For multimaster bringuplaunch, need to load the controller config -->
      <rosparam command="load" file="$(find husky_control)/config/control.yaml" />
    </group>

    <!-- For single master bringup, run robot control on the gazebo master -->
    <!-- Note that husky_description/description.launch is already included in husky_control/control.launch. -->
    <group unless="$(arg multimaster)">
      <include file="$(find husky_control)/launch/control.launch">
        <arg name="multimaster" value="$(arg multimaster)"/>
        <arg name="laser_enabled" value="$(arg laser_enabled)"/>
        <arg name="realsense_enabled" default="$(arg realsense_enabled)"/>
        <arg name="urdf_extras" value="$(arg urdf_extras)"/>
      </include>
      <include file="$(find husky_control)/launch/teleop.launch">
        <arg name="joystick" value="$(arg joystick)" />
      </include> ...