aledged.....
The same reason why a LOT of people get away with calling a party (spokesman, platform agenda, etc etc etc) the democratIC party, instead of the democrat party (spokesman, platform agenda, etc etc etc):
Linguistic laziness and/or journalistic perfidy
Because they need a word to have meaning in their lives.
They don’t care that it means something “actually” as a legal definition or in general
It was manslaughter and they guy should be strung up in my opinion but, words and definitions matter and he will spend 30 years behind bars and be a bitch for anyone who wants his azz