The narcissistic ego manics love showing off in public.
It's the equivalent of hard of hearing old people yelling into their cell phone. An amazing display of self importance.
Siri only impresses those who need to be the center of attention.
I can do anything Siri can, in complete silence, and quite a bit faster.
So NO I have never used that gimmick.
And then there are those of us that find Siri very useful, but are embarrassed to use it in public and therefore avoid it altogether or do so as quietly and discreetly as possible.
One example for me is once a week I give a friend a ride. On my way out the door with my hands fairly full, it's quicker and easier to tell Siri to send him a message stating I'm on my way. That way he knows approximately what time to meet me outside. Sometimes there are other people in the hallway that overhear me, but I try not to be obvious with it.
Not all Siri users are narcissistic.