Why are the Channel Islands linked to the British crown but not part of the United Kingdom?

The Channel Islands are not part of the United Kingdom because they are British crown dependencies, a status that stems from their unique historical connection to the British monarchy rather than incorporation into the British state.12

Following the Norman Conquest of 1066, the islands were part of the duchy of Normandy. When the English crown lost control of mainland Normandy, the Channel Islands remained loyal to the British monarch, maintaining their status as possessions of the crown rather than becoming part of the United Kingdom.1

Because of this, they are not governed by the U.K. Parliament; instead, they are administered according to their own local laws and customs, grouped into the two distinct bailiwicks of Jersey and Guernsey. They also maintain tax sovereignty, though they are protected by British tariff barriers.1