Those of us who grew up on a farm that raised corn definitely do not conform to that convention.

Unless you're talking about eating it, just 'corn' is definitely 'field corn'. Raising it, hauling it, driving by it in the field, grinding it into animal feed; it's just 'corn'.

Picking or buying it to boil or roast and eat? That's definitely 'sweet corn', because you aren't eating 'corn'.