Every few months I try to use Siri. And every single time I reach the same conclusion: Unusable and worthless to me. I don't have a weird accent, a lisp or a speech impediment of any kind. Just plain "clean" adult (as opposed to "like" bubblegum teenager) California English. I have never gotten anything useful out of the technology from the day it was introduced.

Just one data point of course. Yet, I'd be willing to bet that the overwhelming majority of iOS users don't use Siri but for the speech recognition version of fart jokes here and there.