And now, on to modern times
Singing these dumb songs (no offense, Sting) morphed into "guising," which was basically just kids going around in costumes, telling jokes, singing little diddies, and busking for money.
As these customs spread to the States via waves of immigrants, it all came to a halt when the Great Depression, followed by World War II, pretty much took the fun out of everything. But as the baby boomers hit trick-or-treating age, the phenomenon resurfaced. And since literally no one wants soul cakes (again, sorry Sting), mass-produced candy in sensible "fun" sizes took their place.
So! This October 31st, when a gaggle of lil' bastards come knocking at your door, demanding a spread of Butterfingers and Sour Patch Things, tell them, "I ONLY HAVE SOUL CAKES AND I DEMAND YOU SING FOR THEM!"