Fragment shader shows alpha, surface shader doesn't

I have 2 shaders that do the same, which is nothing... just pass the color.

As a fragment shader

 Shader "EffectBakers/FogBaker"
 {
     Properties
     {
         [PerRendererData] _MainTex ("Color (RGB) Alpha (A)", 2D) = "black" {}
         [MaterialToggle] PixelSnap( "Pixel snap", Float) = 0
 
         [HideInInspector]_FogTexture( "Fog Ramp Texture", 2D) = "black" { }
         [HideInInspector]_01FogDepthVerticals( "Linear Depth 01 And Verticals", Vector) = (0.0, 0.0, 0.0, 0.0)         
         [HideInInspector]_IsWarm( "Warm texture or Cold texture", Range(0,1)) = 0
     }
 
     SubShader
     {
         Tags
         { 
             "Queue"="Transparent" 
             "IgnoreProjector"="True" 
             "RenderType"="Transparent" 
             "PreviewType"="Plane"
             "CanUseSpriteAtlas"="True"
         }
 
         Cull Off
         Lighting Off
         ZWrite Off
         Fog { Mode Off }
         Blend One OneMinusSrcAlpha
 
         Pass
         {
         CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag
             #pragma multi_compile DUMMY PIXELSNAP_ON
             #include "UnityCG.cginc"
 
             struct appdata_t
             {
                 float4 vertex   : POSITION;
                 float2 texcoord : TEXCOORD0;
             };
 
             struct v2f
             {
                 float4 vertex   : SV_POSITION;
                 half2 texcoord  : TEXCOORD0;
             };
 
             fixed4 _Color;
 
             v2f vert(appdata_t IN)
             {
                 v2f OUT;
                 OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);
                 OUT.texcoord = IN.texcoord;
                 #ifdef PIXELSNAP_ON
                 OUT.vertex = UnityPixelSnap (OUT.vertex);
                 #endif
 
                 return OUT;
             }
 
             sampler2D _MainTex;
 
             fixed4 frag(v2f IN) : SV_Target
             {
                 fixed4 c = tex2D(_MainTex, IN.texcoord);
                 c.rgb *= c.a;
                 return c;
             }
         ENDCG
         }
     }
 }

And as a surface Shader:

 Shader "EffectBakers/FogBaker"
     {
         Properties
         {
              _MainTex ("Color (RGB) Alpha (A)", 2D) = "white" {}
             _Color("Tint", Color) = (1, 1, 1, 1)
             [MaterialToggle] PixelSnap( "Pixel snap", Float) = 0
     
             [HideInInspector]_FogTexture( "Fog Ramp Texture", 2D) = "black" { }
             [HideInInspector]_01FogDepthVerticals( "Linear Depth 01 And Verticals", Vector) = (0.0, 0.0, 0.0, 0.0)         
             [HideInInspector]_IsWarm( "Warm texture or Cold texture", Range(0,1)) = 0
         }
     
         SubShader
         {
              Tags
             { 
                 "Queue"="Transparent" 
                 "IgnoreProjector"="True" 
                 "RenderType"="Transparent" 
                 "PreviewType"="Plane"
                 "CanUseSpriteAtlas"="True"
             }
     
             Cull Off
             Lighting Off
             ZWrite Off
             Fog { Mode Off }
             Blend One OneMinusSrcAlpha
     
             CGPROGRAM
             #pragma surface surf Lambert vertex:vert nofog keepalpha
             #pragma target 3.0
             #pragma multi_compile _PIXELSNAP_ON  
     
             sampler2D _MainTex;       
     
             fixed4 _Color;       
     
             struct Input
             {
                 float2 uv_MainTex ;
                 float3 worldPos;
             } ;
     
             
             void vert( inout appdata_full v, out Input o )
             {
                 #if defined( PIXELSNAP_ON )
                     v.vertex = UnityPixelSnap(v_.vertex);
                 #endif
     
                     UNITY_INITIALIZE_OUTPUT(Input, o);
                 o.worldPos = mul( _Object2World, v.vertex );
             }
     
             sampler2D _FogTexture;    
             fixed4 _01FogDepthVerticals;
             int _IsWarm;
     
     
             void surf(Input i, inout SurfaceOutput o)
             {
                 fixed4 color = tex2D( _MainTex, i.uv_MainTex );        
                 
                 o.Albedo = color.rgb * color.a;
                 o.Alpha = color.a;
             }
             ENDCG
         }
     
         FallBack "Transparent/Cutout/VertexLit"
     }

why the fragment shader displays the sprite with alpha channel and no problems, but the surface one shows the transparency as black and everything is opaque?

Thanks for the help.