Explicit Slicing of std.container.Array

["Nordlöw" via Digitalmars-d-learn]

Is there a reason why std.container.Array have to be explicitly 
sliced before being processed by range algorithms such as filter 
typically as

     import std.container: Array;
     Array!int a;
     foreach (e; a[].filter!"true") {}

?

Does memory allocation play a role?

I would like to see it be used in replace of D builtin arrays 
without any code changes.