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.

It's many years since I read this but I seem to remember the original impetus for agile was an internal software development team having a mix of longer term goals, and then lots of reactive work/support. Possibly the latter making up the majority.

It was a way to bring some sense of order to what was chaos: new requests coming in all the time, work being dropped partway through to deal with the new requests, little progress on any front.

I think agile works really well in this kind of context by bringing in a sense of discipline and keeping new work at bay until the beginning of the next cycle[1]. It can also help to keep teams delivery focussed in other contexts but, key point, does not obviate the need for additional planning outside the sprint/iteration framework.

The problem really occurs when people treat agile as sufficient on its own, or as the one project management tool to rule them all. Total nightmare, especially with multiple teams involved.

[1] How workable this is in practice is open to question: I can tell you it's not always a great approach in an environment where client projects typically last a few days and on time delivery has been known to depend on a critical bug fix for a legacy codebase. Especially problematic when requests come in either during the launch phase, because there's usually a fairly hard window, or during the reporting phase, because there's a delivery deadline looming.