Actually, it doesn't work just about everywhere (Alexa), it's in english and distribution is not worldwide either. So what IS YOUR POINT. Do you have a point?
As for Alexa, it's only "better" in its niche, not everywhere, far from it. If I call Siri from my watch for example, Alexa has no chance to "beat" Siri. And yes, I have tried it.
The main reason is that it is a new product, with a limited availability at launch that they need to make sure it works 100% well and is supported adequately before risking a wider rollout. They did the same thing for the watch which took a hell of a long time (12 months before being distributed widely worldwide).
Well, my Echo Dot is quite good in understanding my Austrian German, not to say that Amazon provides plenty of localized content. Furthermore it‘s undoubtedly better in English speech recognition than Siri on all my devices.
I have no experience with Google, though.