In Europe, Soccer Leagues Have a Promotion and Relegation System

In Europe, soccer leagues have a promotion and relegation system where the teams in the top league with the worst record at the end of the season are relegated to the "minor" leagues and the minor league teams with the best record are promoted to the majors. Sports infrastructure is significantly less extravagant in Europe than it is in the United States with teams having older, smaller stadiums with less amenities. For example, until recently many English clubs had a significant amount of terrace seating, that is large flat terraces without seats generally used as standing room areas. How can the promotion and relegation system explain this difference?