When is a pie not a pie?

When it’s in a casserole dish!?
Last week a Silent Customer expressed her disappointment when she ordered ‘steak & Ale pie’ and received casserole in a dish with a puff pastry top. She marked the pub down for not serving what was described on the menu and I changed it saying that many people DO accept this as ‘pie’. But this made me think: Should the definition of 'pie' be subjective?
According to the British Pie Awards 'A pie is deemed to be a filling totally encased in pastry'. So, why do most pubs serve what they call 'pies' in casserole dishes? Is it that most people prefer casserole with a lid that just shatters into a thousand tiny pieces as soon as you stick a fork in it? Or is it that chefs don’t serve short crust pastry pies because there is a higher wastage risk and they are more labour intensive?