CPP13 — Constructor for structures?

The mapping for user exceptions and structures is identical, except
for one thing: user exceptions have an additional constructor with
one parameter for each member, so I can construct and throw the exception
with a single throw statement.

However, structures are second-class citizens: I can't instantiate and
initialize a structure at the same time. (Well, at least not in general,
because static initialization only works for aggregates and, at any rate,
I can only instantiate and initialize with compile-time constants.)

So, why don't we add the same constructor to the mapping for structures?
It seems inconsistent to have one mapping for structures and a slightly
different one for exceptions, when in fact they both could be the same.