These were political reasons. The Chinese (Beijing) do not accept Taiwan as an independent country. That is why they did not like when airlines flew to Taiwan. That is the reason that many European airlines (including e.g. Swissair, KLM) founded these "Asia" airlines. Swissair flew with its two Asia MD 11 to Taiwan and to other countries but not to Beijing. Once I even saw a Swissair Asia at JFK.