Declare and Define Before Use? [rant]

[kdevel via Digitalmars-d-learn]

Why are people writing

   import std.stdio;

   void main ()
   {
      S s;
      s.foo;
   }

   struct S {
      void foo ()
      {
         writeln ("a");
      }
   }

but not

   void main ()
   {
      S s;
      s.foo;
   }

   struct S {
      void foo ()
      {
         writeln ("a");
      }
   }

   import std.stdio;

?