@engine posted a link, showing that less than 0.1% of all websites are using AMP.
Statistics can be very misleading. Look at the graphs in the link carefully. Spefically the third graph, where x axis = number of websites and y axis = volume of traffic to those websites. AMP fall in the top left of the graph. Few websites use AMP, but those that do tend to be high traffic sites. You can interpret this tow ways, one using AMP will increase your traffic, that would be awesome if it were true, but it is not. Or, many high traffic sites have implemented AMP. The latter seems like a more plausible explanation. I think this goes to my comments above, a proper AMP implementation is a complex undertaking that most webmasters (specifically the WP type that do not code or understand complex JS) do not have the knowledge, the skill or the desire to undertake something like AMP. But big sites, like big news sites, definitely see the benefit and have and are making the big investment to implement AMP.
Love it or hate it, I think that something like AMP, will continue to forge the divide between the small and the big players. This will make it ever harder for the smaller sites to compete. In the future as AMP and PWA's become more and more prevalent the lines between apps and websites will become more and more blurred, and running a plain vanilla website will be as out of place as having a website styled with tables is today.
The only thing holding this back right now is Apple's reluctance to adopt service-workers. Once (or if) that happens the flood gates will open and the web will change overnight.