Actually, betel was consumed in quite large quantities in the coastal areas of south China right up to the early years of this century and still today in Taiwan. It was sent as tribute to the Chinese court from Champa in the 10th and 11th centuries, and in the 19th century there are records of "huge cargoes" leaving Penang and Singapore for China. Grace Wong has written about the importance of betel as a substantial part of the homeward-bound cargo in the porcelain trade. The trade was in the hands of Chinese merchants mainly, and Chinese immigrants operated the huge areca plantations on the island of Penang. Penang, in fact, is the Malay word for areca palm.
All over Southeast Asia betel chewing used to be (and in many places still is) of enormous importance as a social ritual - perhaps a bit like tea ceremonies in China and Japan. But in Southeast Asia betel has a substantial religious and mythological function, too.
In Vietnamese Ceramics by Stevenson and Guy, there's a nice appendix (pp. 391-395) by Philippe Truong about the symbolism of Vietnamese ceramic limepots that are very similar to Trieu's.
Research: LH Mak