Why switch's textOn and textOff are not displaying?

First of all you should use SwitchCompat in order to make it compatible with all android versions and have the nice look of material design of the switch.

Back to your problem, you are missing an attribute for showing the text -app:showText -, here is an example:

<RelativeLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  ...>
    <android.support.v7.widget.SwitchCompat
        android:id="@+id/switch_compat"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="50dp"
        android:layout_marginStart="50dp"
        android:layout_marginTop="25dp"
        android:checked="false"
        android:textOff="OFF"
        android:textOn="ON"
        app:showText="true"/>
</RelativeLayout>

Text is not shown by default under Material theme.

You can change it using the android:showText property

<Switch
    android:id="@+id/itemListSwitch"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textOn="Vibrate on"
    android:textOff="Vibrate off"
    android:showText="true" />