Food production isn’t some homogeneous entity, it might make sense to subsidize some level of staples but direct subsidies are more transparent and can be more easily limited. But, obviously industry doesn’t want the government feeding through to stop simply because the’ve scaled vastly past domestic consumption.

Similarly, military procurement can subsidize relevant industries without impacting the wider economy. In other words you can maintain some domestic steel production etc without impacting the cost of goods.

I think that under-appreciates the slippery slope of political leverage. There's a reason Iowa is so hell-bent on keeping their primaries first.

Without explicitly and financially tying subsidy-fueled gains to modernization efforts, market participants begin to consider the subsidies as business as usual, plan around them, and get lazy.*

It removes a primary incentive to maintain pace with global technology improvements. Domestic industry whispers in politicians' ears that their global competitors are unfair for reasons X, Y, and Z, and they really need more subsidies to protect them.

{Benefit from politically driving new tariffs / subsidies} must never be higher than {benefit from investing in efficiency increases}.

* Lazy as measured by peak international efficiency, not work. E.g. a farmer who works their ass off manually farming is economically inefficient compared to one who mechanizes most of their work