How to make a custom shader affected by Ambient Light

I made my own shader since I wanted to us 2 textures in which I'll lerp between them. However, the ambient light does not affect them. May I know what I'm missing here?

 Shader "Custom/CrossMaterial" {
   Properties
   {
     _Blend ( "Blend", Range ( 0, 1 ) ) = 0.0
     _Color ( "Main Color", Color ) = ( 1, 1, 1, 1 )
     _MainTex ( "Texture 1", 2D ) = "white" {}
     _Texture2 ( "Texture 2", 2D ) = ""
   }
   SubShader
   {
     Tags { "RenderType"="Opaque" }
     LOD 300
     Pass
     {
       SetTexture[_MainTex]
       SetTexture[_Texture2]
       {
         ConstantColor ( 0, 0, 0, [_Blend] )
         Combine texture Lerp( constant ) previous
       }   
      
     }
   
     CGPROGRAM
     #pragma surface surf Lambert
     
     sampler2D _MainTex;
     sampler2D _Texture2;
     fixed4 _Color;
     float _Blend;
     
     
     struct Input
     {
       float2 uv_MainTex;
       float2 uv_Texture2;
     };
     
     void surf ( Input IN, inout SurfaceOutput o )
     {
       fixed4 t1  = tex2D( _MainTex, IN.uv_MainTex ) * _Color;
       fixed4 t2  = tex2D ( _Texture2, IN.uv_Texture2 ) * _Color;
       
       o.Albedo  = lerp( t1, t2, _Blend );
     }
     ENDCG
   }
   FallBack "Diffuse"
 }