This risks me sounding like a smug arse, so apologies if that's the case. It's not meant that way.
My mum (and her mum before her) had a very old school cooking approach. They were skint. Grandad was a poacher.
Pies are a way to make cheap ingredients go further. The economy comes from buying a cheap cut of meat that's roasted slowly on a Sunday, and then chucked in with a load of old (about to go off) veg to make a pie filling, stew, and casserole to feed the family for another three nights. In this context, a bit of butter and flour, a few potatoes, or some suet (dumplings) are all cheap ingredients to stretch out the cheap meat.
(Appreciate butter is v expensive atm. Wasn't always the case)
Buying the ingredients for a pie in isolation, never mind the man hours and oven running costs, is not economical at all. Shop bought does make more sense.
In my (old fashioned - I'm not a Tory, honest) view, this is why we have such a skewed food system and economy. We don't have the time or the resources to cook like this any more. My granny was poor, could make a mean pie, but didn't have to earn half the household income whilst simultaneously doing home exonomics magic.
I LOVE cooking. But I work full time and we're still mostly skint. It's a circle I can't square.