Lovecraft's take on why we are so entranced by things like Halloween

From his essay, "Supernatural Horror in Literature", 1927

"The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown... Because we remember pain and the menace of death more vividly than pleasure, and because our feelings toward the beneficent aspects of the unknown have from the first been captured and formalised by conventional religious rituals, it has fallen to the lot of the darker and more maleficent side of cosmic mystery to figure chiefly in our popular supernatural folklore. This tendency, too, is naturally enhanced by the fact that uncertainty and danger are always closely allied; thus making any kind of an unknown world a world of peril and evil possibilities. When to this sense of fear and evil the inevitable fascination of wonder and curiosity is superadded, there is born a composite body of keen emotion and imaginative provocation whose vitality must of necessity endure as long as the human race itself. Children will always be afraid of the dark, and men with minds sensitive to hereditary impulse will always tremble at the thought of the hidden and fathomless worlds of strange life which may pulsate in the gulfs beyond the stars, or press hideously upon our own globe in unholy dimensions which only the dead and the moonstruck can glimpse."