Traditionally, it's because some rich groups are trying to rig markets in their favor. Read up on the sugar cartels, and the US corn lobby for the canonical ex

Traditionally, it's because some rich groups are trying to rig markets in their favor. Read up on the sugar cartels, and the US corn lobby for the canonical example. The sugar cartels were (are?) the world's most powerful cartel, but the corn lobby in the US is similarly large. Even after the cartels take their profit cut from artificially inflating the price of imported sugar, it's still cheaper than domestic sugar or high fructose corn syrup. So, the corn (and probably sugar) lobby paid congress to create massive import tariffs on sugar. Later Coke and Pepsi switched to domestic HFCS in the US in response. These days, we know that HFCS is one of the root causes of the obesity epidemic, but it would be political suicide to let a 5-10 year reduction in population-wide life expectancy get in the way of the corn lobby's profits. Similar stories exist for pretty much all tariffs. For instance, when the Trump admimnistration increased tariffs on China, they also snuck in tariffs on wood from Canada. A very small group of people (that backed Trump in the election) control most of the wood production in the US. The tariffs created a supply crash of lumber in the middle of the covid construction boom. At some point, the price of a plywood board was above $100 (up from ~$20 or less). Most of that translated directly into profits for the timber companies. Of course, it also contributed to the housing shortage, but homeless people don't fund political campaigns, so that didn't really enter into the decision making process. (edit: I realized that was unnecessarily partisan. Biden renewed/expanded the tariffs I'm complaining about.)