Well, I don't know about other areas of software development not having feature creep. Just look at the "feature set" in MS Office. I don't much care for MS, but you can't really fault them on the methodology side of things. There are far more relevant factors that determine whether features creep into your system than whether you had a formal design process or not. Spelling out all the features you're going to have before you start coding doesn't mean you don't have a lot of feature that added little to no value or even adversely impacted the value added.