Agile works well for redecorating a house (“let’s paint the walls first, and worry about the couch later”), less so for building one. That requires more foresight, larger-scale planning, and writing things down.

With agile, building houses still somewhat works because people will do that planning in their heads. So, knowledge will end up _only_ in people’s heads, not even in everyone’s heads, and will deteriorate there, even if those people do not leave the project.

So, by the time it’s time to do a large-scale update to the house (add a room, update ventilation to modern standards), nobody knows where the ventilation ducts run, why one of them is so much larger, that there’s asbestos in the ceiling, etc.

And of course, some people try to use agile not for building houses, but for building apartment blocks.