> One factor that comes to mind: lack of automated tests These tests have to be at the right level. Unit tests are the easiest to write, but unit tests can be

> One factor that comes to mind: lack of automated tests These tests have to be at the right level. Unit tests are the easiest to write, but unit tests can be pretty brittle. Reorganizing the codebase can result in many unit tests breaking (or being made redundant), which might lead to stagnation from fear of breaking tests (and the extra work of fixing them). System tests are much harder to write, but are invaluable during a major refactoring. You want to be sure that you're not changing the behaviour of the system while changing its structure. The V-model is (IMO) an underappreciated tool in the development lifecycle.