Multi-hour delays at European borders were not unusual before, and persist at the external land borders of the Schengen area. The common currency is valuable f

Multi-hour delays at European borders were not unusual before, and persist at the external land borders of the Schengen area. The common currency is valuable for more than just tourism purposes. A business in one country can much more easily trade with businesses in other countries if it doesn't have to deal with currency risk and the resultant necessary hedging, and if the business is selling services to consumers the single currency allows them to compete with businesses across the whole Eurozone on a level playing field. That's just considering currency; the single market is of course a much broader concept.