Tax breaks for specific activities are by dentition a subsidy by lowering costs.

If people with blue eyes suddenly did not have to pay taxes then that would be a massive subsidy. If you get a pay check and the taxes are already taken it it's just as much 'your money' as if you got the full paycheck then had to pay taxes after the fact. The point is more money goes out of your paycheck because the US government subsidizes other and often very rich people.

Sorry for my ignorance but is this merely a technical distinction? I would have thought tax-credits, and non-deduction are effectively equivalent?