Once upon a time there was a kindly old witch who hated children. This is not an uncommon sentiment among old witches, or even old people in general, who often find themselves at odds with those younger than they are. This old witch, however, had a very specific reason for despising children - they kept trying to eat her house.
The witch, whose name was Beatrice, lived in a magical cottage made from gingerbread and sugar, which she had constructed in the deepest, darkest part of the old haunted forest. The animals of the forest knew better than to try to eat the delicious house, but human children who had been abandoned there by their parents were forever gnawing on the eaves and smashing the sugar windows so that they could suck on the jagged, glittering fragments. It drove the old witch crazy.
Beatrice tried leaving out freshly-baked goods in little parcels tied up with string hanging from nearby trees, like bird-feeders for wayward children, but the wretched little urchins always ignored them and went straight for the house. She tried ornamenting the exterior of the house with licorice, which was the most inedible candy item that she could think of, but even that didn't discourage the children. She even tried entreating the spirits of the restless dead to lurk in the shadows around her house and fill the air with the unearthly chill of death. Nothing worked.
Then, one horrible day, an orphanage in a nearby town burned down. It was a slow-moving fire, and the incident occurred during the day, and so all of the children survived. The owners had nowhere else to put so many orphans, and so they abandoned them all in the forest. Beatrice was horrified to look our her window and see that the house was beset by dozens of children, swarming over it like locusts. She ran out and shouted at them and turned several of them into frogs, but the rest could not be dissuaded from their feast, and in a matter of minutes the whole building was structurally unsound.
Now witches can be a solitary breed, aside from the occasional coven, but no matter how isolated a witch might be, they can still depend on their fellow witches in times of great need. The severity of their circumstances is measured on the Salem Memorial Index of Witch Peril, which somewhat confusingly ranges all the way from "One" to "Dorothy."
Of course, no one had tried to melt Beatrice or dropped a house on her sister, so she didn't rank anywhere near "Dorothy", but being rendered homeless by a swarm of ravenous orphans put her all the way up to "Orange." It really is a very eccentric system.
The nearby witches certainly weren't going to leave one of their number out in the cold, especially not cold that was supernaturally chilled by the restless dead who still flitted about in the shadows of the ruined house. They determined that the quickest way to supply new building materials would be to steal some from less important existing buildings, and so everyone partially dismantled their barns and tool sheds and whatnot and sent along walls and doors and such. One witch even contributed the roof from her gazebo.
The end result was a hideous patchwork building that looked like it belonged to a crazy person. The pieces came from many different kinds of buildings, constructed in a variety of styles, and no two were made from the same sorts of materials. She had a wall of sponge cake, a door carved out of marzipan, and even a few bits made out of less traditional substances, like wood or stone.
While a gingerbread house clearly owned by a witch was somehow irresistible to children, the new house apparently exuded such a strong sense of wrongness that children were unwilling to go anywhere near it, in spite of the fact that pieces of it were clearly edible. Beatrice was overjoyed! The patchwork house was only meant to be temporary while Beatrice baked herself a new gingerbread house, but she decided that putting up with its eccentricities was worth not having to worry about children gnawing on it all the time. It's not as if anyone expected to get their contributions back, so that wasn't a problem.
Actually, many of the witches who had come to Beatrice's aid found her decision to live in such a strange dwelling to be a bit of a revelation. Why had they been living in confectionery all this time? They weren't necessarily going to go to the extreme of living in a house made of eleven different things that didn't really go well together, but why couldn't they live in houses made of wood, or stone, or brick? Did they even have to live in the middle of haunted forests?!
And so now witches live in houses made of whatever they want, in villages and towns and cities, and you can never tell if one of your neighbors might secretly be a witch. I advise you to err on the side of caution - don't eat other people's houses.