Final answer:
Political considerations are a major reason why trade restrictions exist despite the resulting inefficiencies.
Step-by-step explanation:
The best explanation for why trade restrictions exist in the real world despite the resulting inefficiencies is political considerations. Political factors often play a significant role in trade policy decisions, as governments must balance the interests of various stakeholders, including domestic industries, labor unions, and consumer groups. Trade restrictions can be implemented to protect domestic industries from foreign competition, appeal to certain voter groups, or address national security concerns.