That said, Dutch governments seem determined to make Schiphol (Amsterdam airport) a hub, and from what I understand, they've succeeded in becoming a hub for not just Netherland, but also the UK, because Heathrow is unable to become a hub due to space constraints. Schiphol, on the other hand, has seen major expansion (a fifth take-off lane in the 1990s), and the Dutch government is considering turning a small airport in the vicinity (Lelystad) into an extension of Schiphol. Most people don't like that idea.
Frankfurt is also a major hub. There are plenty of hubs, but there isn't always space for them (like in London), and other concerns are often deemed more important than sacrificing all space to an airport.