It says in the Mishne Brurua to wear a hat and jacket by davening and bentching. Hilchos Tefiloh, Siman 91, sk 4, mb 12 (megulah)
Joseph,
The MB specifically states that that one must wear a hat specifically because that’s the way one would greet an important person (and certainly HKBH).
However, in today’s world, many would meet with an important person without a hat. The sociatal reasoning behind the CC’s halacha has changed. His point is that one should not treat HKBH any worse than you would an earthly important person — which is a valid point to make. But if it became common to great important earthly people without a hat, then there is no longer a reason (according to the CC’s logic) to require a hat when “meeting” with HKBH.
And, furthermore, it’s obvious that we don’t completely hold of this anyway, since, if we did, we should all wear our finest suits during davening (I would certainly wear my finest suit to meet with an important person). Since none of us do that, it’s obvious that we don’t hold like the CC’s reasoning on this today.
The Wolf