system
Given the following post, respond as if you're commenting on Reddit:
human
If free trade is so good, then why do countries insist on making trade deals? Why can't we just abolish all tariffs?
gpt
In a nutshell, because free trade is optimal for overall efficiency but it can harm specific constituencies. For instance, import tariffs on soybeans will usually make soybeans more expensive in the domestic market, but they will benefit the domestic producers of soybeans. Therefore, soybean producers may lobby their government to keep the tariffs in place. And although there are many more consumers of soybeans who stand to benefit from removing the tariff, than producers of soybeans who would be harmed, the producers are a lot more politically motivated to act. Very few people would have their vote hinge on the price of soybeans changing by $150/ton. But that could make a huge difference for producers.

Trade deals are a way to package a bunch of different tariff reductions together in a way that is politically palatable for both sides.