The only custom shader not getting Shadow

Shader "Custom/1_displayImageOnSlide" {
    Properties {
        _MainTex ("Texture", 2D) = "white" {}
        _CutoffX("CutoffX", Range(0.0,1.0)) = 1
        _CutoffY("CutoffY", Range(0.0,1.0)) = 1
    }

    Category {
        Cull off
        Blend SrcAlpha OneMinusSrcAlpha
        Lighting Off
    Fog { Mode Off }

        SubShader {    
//      Tags {"LighMode"="ForwardBase"}
        Tags {"Queue"="Transparent" "RenderType"="Transparent"}
        //UsePass "VertexLit/SHADOWCOLLECTOR"    
        //UsePass "VertexLit/SHADOWCASTER"

        CGPROGRAM
        #pragma surface surf Unlit 
        //#pragma surface surf Lambert

        // Inside CGPROGRAM block.


        half4 LightingUnlit (SurfaceOutput s, half3 lightDir, half atten) {
                half4 c;
                c.rgb = s.Albedo;
                c.a = s.Alpha;
                return c;
        }

        sampler2D _MainTex;

        struct Input {
                float2 uv_MainTex;
                float4 color : Color;
        };

        fixed _CutoffX;
        fixed _CutoffY;

        void surf (Input IN, inout SurfaceOutput o) {

        half4 tex = tex2D(_MainTex, IN.uv_MainTex);

        o.Albedo = IN.color.rgb * tex.rgb;
        o.Alpha = IN.uv_MainTex.x > _CutoffX ? 0 : IN.uv_MainTex.y > _CutoffY ? 0 : IN.color.a*tex.a;
        }
    ENDCG      
        }//sub Shader End
    }//Categoy End
     FallBack "VertexLit"    // Use VertexLit shadow caster/receiver passes.
}

      

        
        
        
      

    

This is my shader file code and applies to the cube object. The problem is the shader is casting the cube correctly, but the cube is not getting the shader. What's bad about it? I do not have enough knowledge about shader programming, so you are invited to share you with a description