> It works and is needed. Where is the problem?
The problem is, tariffs don't really work. Not in the long-term.
Tariffs can hurt local producers too. If a company is just so efficient at producing good that they can produce cheaper products inclusive of the tariff, then the local company has no chance. They have no hope of expanding outside of their local markets and they will eventually give up.
Most of the time, tariffs merely act as extra profit margin at the expense of the local economy. So the local company has no incentive to improve. So, in the long-term, tariffs on imported goods are are effect way of destroying local industry. It often drives the competition to fiercely optimize their production, making them substantially more competitive on a global market.
The only time tariffs are effective at protecting a market, is when that market only exists locally, not globally. Thus, preventing any producers from gaining efficiency on the global market before tackling a domestic one.
If you want the government to prop up a local industry, get the government to purchase a large volume of goods from them at a fair, but highly-competitive price. Then the producer has incentive to optimize production because they know exactly how much they can save each year. Decades of small incremental improvements add up.