City churches are sometimes quiet and peaceful solitudes, caves of silence where a man can seek refuge from the intolerable arrogance of the business world. One can be more alone, sometimes, in a church than in a room in one’s own house. At home, one can always be routed out and disturbed (and one should not resent this, for love sometimes demands it). But in these quiet churches one remains nameless, undisturbed in the shadows, where there are only a few chance, anonymous strangers among the vigil lights, and the curious impersonal postures of the bad statues. The very tastelessness and shabbiness of some churches makes them greater solitudes, through churches should not be vulgar. Even if they are, as long as they are dark it makes little difference.
Let there always be quiet, dark churches in which men can take refuge. Places where they can kneel in silence. Houses of God, filled with His silent presence. There, even when they do not know how to pray, at least they can be still and breathe easily. Let there be a place somewhere in which you can breathe naturally, quietly and not have to take your breath in continuous short gasps. A place where your mind can be idle, and forget its concerns, descend into silence, and worship the Father in secret.
There can be no contemplation where there is no secret.
— Thomas Merton, New Seeds of Contemplation
UPDATE: Another reason to make a habit of visiting empty churches: if there is more traffic within them, desecrations and thefts are less likely to occur.