Why would the U.S. impose a voluntary export restraint on Japan for textiles instead of using a import quota or tariff?
Why indeed. This is as much an international political question as a question in economics. Quota or tariffs tend to apply to all nations rather than a single nation. Second, the US is a participant in GATT and WTO (international trade agreements), which restrict tariffs and quotas. Third, what is Japan getting for agreeing to voluntary restraints?