Same reason Latin is used for Scientific and biblical--a "dead" language no longer spoken by a regional population--no slang or changes/inclusions over time. English is spken by americans, Australians, and New Zealanders but there are major differences/inclusions in each region, not to mention Ireland, Wales, and Scotland. Pants in the US are trousers in the UK, so if you tell a Brit women you like her pants, you'll probably getsmacked for talking about underwear. Pissed is drunk in the UK and upset here. Things morph/change, change being the only constant in our universe. I ban you for being so inquisitive, that's my "sthick". (thing)