For me it's mostly about knowing what you're getting when craving the flavour of a particular dish. Carbonara is perhaps an example of a recipe that's turned too rigid, but I've also ordered it and been served diced boiled ham in bechamel - an affront to anyone with their sights set on pan-fried pork and a rich, fatty mouthfeel.

Everyone has their own personal limit and variations are allowed within certain unwritten boundaries. Swedish meatballs, for example, can be varied in many ways - but if you put garlic in them, I think you should call them something else.