While the faithless ask for an angelic visitation to consume it upon their lusts, the Lord does not send angels to the faithless. The sign seeker gets no sign because the Lord has nothing to prove. Indeed, the sign seeker is the one who has something to prove to the Lord, not the other way around. Unless they prove to the Lord through obedience and humility that they are worthy of it, they will never have faith strong enough nor a mind firm enough to deserve an angelic visitation.
Thus, angels don’t come to replace or bolster faith. They come to those whose faith is so strong that it would not be affected by such a visitation.
Hugh Nibley
“…people of firm mind and strong faith are the only ones an angel can come to. Otherwise, it will set you off your rocker. Remember, Brigham Young said, ’Pray that you will never see an angel,’ because almost everyone who has seen one has apostatized. It’s more than they can take.” (Ancient Documents and the Pearl of Great Price, p. 6)