Tariffs do decrease competition and lead to higher prices for consumers....but...there are certain industries important for national security where a country may wish to subsidize an industry like building renewables or use a tariff against a country like China that is trying to corner the market through nationalized companies. Because those companies are a wing of their government (so to speak) a free market company can't compete and eventually all you have are Chinese companies for these critical industries and they can dictate policy to us.