Expressions in initializers

[Harold Rabbie]

Here's one for the comp.lang.c.lawyers - K&R 2 says (without explanation)
that non-constant expressions can be used as initializers only for static 
scalars, not for automatics, and not for aggregates.

e.g. I can say:

static double x = sqrt( 2.0 );

but I can't say:

void foo( void ) 
{
    double x = sqrt( 2.0 );
}

nor can I say:

static struct foo {
    double x;
} bar = { sqrt( 2.0 ) };

What's the deal here - is ANSI easing up on those no-good implementers :-)
or is there a valid reason for this restriction?

P.S. No need to FAQ me over on this one.