Ever tried to opt out of Siri? I have. It nags you constantly. You search, looking for a gist to nuke it, but what you find doesn't work. Finally, you give in, just to get the damn thing to shut up.
I don't even remember Siri also exists on Mac OS most times.
I guess I'm in the wrong leg of the A/B test. Fing fantastic.
You could try to delete all of the preference files:
find ~/Library/Preferences/ -iname com.apple.siri\* -delete