Asian or Oriental?

[SunsetBengal]

Why is it considered bad form to refer to people from SE Asia as Oriental? I understand that Asian is now the preferred term of reference, but I'm not sure it means what everyone intends it to mean. When a person says "Asian", the common thought is a person of Chinese, Japanese, Korean, etc. decent. But alas, there are more Countries in Asia, and those people look nothing like the stereotypical "Asian" person. I mean you have people from Russia, India, and many more, and they look nothing like the people commonly associated as being Asian.

So, why can't we still use "Oriental" to differentiate?