Because....(some reasons I can think of) lol
• Ignorance
• A lot of people don't realize that Asian and Pacific Islander are just geographical-terms...mistake is made when people associate these terms with ethnicity and race...
• Another possible reason is because of "Asian" being synonymous to East Asians especially in America...
• Some Asians (East Asians) don't like Filipinos calling themselves Asians because they are very different to them..lol...(Heck.. Iranians, Kazakhs etc. are 'Asians" too)
• Filipinos and Pacific islanders (Micronesians, Polynesians) descended from a common ancestor (Austronesian people via Taiwan) some Filipinos may think that being related makes Filipinos Pacific Islanders too...No...Pacific Islander is just a geographical term...
→ http://www.youtube.com/watch?v=mYSr2k4buqU
• Philippines is technically an archipelago (Islands) in the Pacific but it is in "Southeast Asia" which makes Filipinos Southeast "Asian"...Maritime Southeast Asian to be more specific...
• You don't have to be East Asian or look like it to qualify as "Asian"...Asia is the biggest continent and consists of many ethnicities and cultures....
Listen to these Filipinos → http://www.youtube.com/watch?v=Qoq_3EKjJ_k