Answer: because the British was Neglecting them and raising taxes
Explanation: they we're being neglected by the king and basically started their own form of government. The taxes was getting out of hand for them ( like tea) so they said " we no longer wanna serve under your rule" and wanted to be their own country. At the time Britain and other countries were at war with napoleon ( i think), which is why they were neglected and why taxes were raised ( that's why we drink coffee instead of tea)