Why forbid "INSERT INTO t () VALUES ();"

[Fabien COELHO]

Hello devs,

I would like to create an "all defaults" row, i.e. a row composed of the 
default values for all attributes, so I wrote:

  INSERT INTO t() VALUES ();

This is forbidden by postgres, and also sqlite.

Is there any good reason why this should be the case?

--
Fabien.