There are two common ways in which I've seen this happen. In one, the code started simple and evolved in place to accommodate bugs or additional use cases. Som

There are two common ways in which I've seen this happen. In one, the code started simple and evolved in place to accommodate bugs or additional use cases. Some refactoring has happened in the past, and that added some complexity to the overall project, but still not all of the abstractions were right. Further refactoring may have been attempted, but proved too involved given the value of the task at hand and the complexity the code had already acquired. The code is now more complex further raising the bar for refactoring when the next change comes along. In the other, substantial effort went into designing the code to be flexible. It was recognized that not all use cases could be understood at the outside, and that refactoring things mid project often fails due to time constraints. A design was arrived at best on the most complete understanding of the requirements at the time, and that naturally design had a certain amount of intrinsic complexity to it as the requirements were complex. As development progressed, it was discovered that the design was not ideal for the actual requirements of the project. Plumbing was added and layers were tacked on to work around the issue. What I conclude from this that you're damned if you do and you're damned if you don't. Practically, I generally prefer working with code that was arrived at by the first approach. It often has a few good abstractions in along with a bunch of methods or classes that just combine too much stuff in one place. Perhaps some things are plumbed into places they shouldn't be. This can, with time and patience, be peeled apart into something a bit more manageable. By contrast, my experience with the second strategy is that it leads to a much less manageable mess where most time is spent finding the code that actual does anything. There is much more plumbing to rip out and seeming innocuous changes have far-reaching consequences.