The main reason for creating a European Market was the growing international competitiveness. In the mid of the eighties the European countries recognized that in the long run the national economies alone won't be able to compete against countries like the US, Japan and the new industrial centers in East Asia. The biggest advantage of the European integration is the unique chance of causing significant economic growth in the member countries by abolishing all kinds of barriers e.g. customs controls, trade restrictions, liberation of the movement of capital, tax harmonization, and by the opening of the financial market, a common trade policy, a common service market, common legal protection of companies and so on.
The two countries who support the European integration most (at least their governments) are Germany and France. One reason therefore might be that both countries have a dramatic increase in unemployment rate within the past few years.
In Baden-Württemberg for example, the area where I am from, the unemployment rate has gone up from about 4% in 1992 to around 9% nowadays. Most likely Mr. Chirac's and Mr. Kohl's only solution concerning the unemployment is a fully integrated economy which for sure would create new jobs in Europe.
The German population, however, is scared that a United Europe would create new jobs only in low wage countries like e.g. Portugal. Many think that a European market with no barriers would would even cause "job hollowing out" of Germany. Moreover the German population likes the strength of the D-Mark and is worried that a single European currency would be weaker. As a result of this many Germans change their money into Swiss Francs. So far Switzerland has done quite well by not taking place in all events available. One reason why they are better off is...