They use chemicals, but they are regulated differently. Herbicides can be used to kill weeds, but not as pre-harvest desiccants. In the US and Canada glyphosate and reglone are often used on food crops as desiccants, causing the chemicals to end up in the food we eat. The style of farming is also quite different, focusing more on grains and potatoes rather than oceans of corn and soybeans, which reduces the need for herbicides.
As far north as I live, most vegetables are grown indoors, so weeds and insects aren't an issue. It does cause the vegetables to be low in nutrients, though.