Refundable tax credits are the thing invented to erase the distinction. That's the "refundable" part. If you would have paid $100 in taxes and you got a $1000 refundable credit then you're paying -$900 in taxes and the government sends you a "tax refund" check.
Which is effectively the same thing that happens even with non-refundable credits for large conglomerates, because they were paying enough in taxes from their other business units to eat the whole thing, while they're still consuming other government services. In order to make that fair to smaller companies and individuals, someone with a non-refundable credit that they couldn't use should be able to sell it to an unrelated business who could use it. But then it would just sell for approximately its face value and affect the government budget in exactly the same amount as if it was a refundable credit, which is why tax credits should always be refundable.
Which is effectively the same thing that happens even with non-refundable credits for large conglomerates, because they were paying enough in taxes from their other business units to eat the whole thing, while they're still consuming other government services. In order to make that fair to smaller companies and individuals, someone with a non-refundable credit that they couldn't use should be able to sell it to an unrelated business who could use it. But then it would just sell for approximately its face value and affect the government budget in exactly the same amount as if it was a refundable credit, which is why tax credits should always be refundable.