I agree with Daeloream. Colonialism was a driving factor. There is this theory proposed by Stanley Mintz and later summarized by Marshall Sahlins that suggested tea and other soft drugs (coffee, sugar, tobacco, etc.) drove Western colonialism in the desire to try to please ourselves due to the entrenched misery of Judeo-Christian beliefs. The two articles are "Sweetness and Power" by Mintz and "The Sadness of Sweetness" by Sahlins. Both are worth a read and are extremely interesting.