The irony of Racism

Me and a friend of mine are at work and we were talkin bout race and whole bunch of other shit that goes on this late...and this thought came to my mind: why are chinese and korean and the countries around them people called "asians" when russia india and a couple other countries are in asia as well...why arent they called asians too?? idk why that came to my head but im glad it did....
if someone can give me a lil insight maybe we can enlighten some people.