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

That’s a big part of why it happens, but every industry wants subsidies the idealized place of “farming” in the American public’s perception make this significantly easier.

That helps explain why chips, cars, airlines, banking etc get subsidized but PVC pipes don’t.