Drucraft Houses are essentially magical aristocracy, and like the regular aristocracy, their origins go back thousands of years.
Drucraft requires sigls, and sigls require Wells. Drucrafters with reliable access to Wells have a significant advantage over those who do not. As such, with the spread of drucraft came competition among its practitioners. Those drucrafters strong, rich, or lucky enough to gain control of a powerful permanent Well would have had a vested interest in maintaining that control. But how? A raider can drain a Well’s essentia in an hour; perhaps a very few drucrafters might have had the resources to place a standing guard on a Well for 24 hours a day, 365 days a year, but for most, such a solution would have been far out of reach. All of these drucrafters would thus have been faced with the same problem: how do you protect something that can’t be moved?
The answer is: you live on it. All across the world, drucrafters independently figured out the same solution: you build a house on top of the Well and move in. Now, instead of having to protect your home and your Well separately, you can do both at once. Plus, as a side benefit, living on top of the Well is going to make you extremely familiar with its nature and quirks; when the time comes to use it shape a sigl, you’re likely to do a much better job, and this advantage will only grow over time.
With reliable access to a powerful Well and with better-quality sigls, these drucrafters naturally prospered. Their children grew up better-fed, better-protected, and better-taught; being raised in the presence of a Well and with a drucrafter parent to instruct them, it would be natural for them to learn drucraft skills themselves. Upon their parents’ death, they would inherit the Well (along with their parents’ property and sigls); in time, they would have children of their own and the cycle would continue. As the families grew in wealth and in size, the Well houses grew with them, going from simple one- or two-bedroom shacks to sprawling estates and mansions.
The full story of the development of drucraft Houses is a very long one, but the above paragraphs sketch out the core of it. The possession of a Well and of the skills to use it evolved into an institution with the family and Well at its core. Individual Houses would rise and decline; many were destroyed, either by wars, the schemes of rival Houses, or (most of all), by fratricidal succession conflicts. But the nature of Wells and of drucraft ensured that whenever one House fell, another would rise to take its place, benefiting from the same feedback loop of generational wealth and knowledge until it would fall and be replaced in turn.