Why do nations practice protectionism?

By getting government to impose import restrictions, producers get higher prices without having to improve their competitiveness. Protectionism is achieved by governments imposing the laws that restrict imports, including tariffs on imported goods, restrictive quotas, and a variety of other government regulations.

Explanation:

If you are taking the Plato test: Nations practice protectionism to prevent loss of jobs and livelihoods, to encourage growth of new industries and to retaliate against unfair trade practices.

the answer is variable

first, the romans stayed isolated because they had to defend their own territories from neighboring cities that were harassing them, like the etruscans. second, once the romans managed to defeat their neighbors, and started to expand their territory, they started to build roads and bridges. finally, now that the romans have covered their territory with roads functioning as highways, they could mobilize their legions faster to assemble larger military units in a specific place.