It reminds me of 2-3 years ago, where almost every Javascript tutorial was littered with JQuery library function calls. Most Stackoverflow questions were answered with JQuery answers. In the meantime things have obviously changed for the better.
With Three.js it's still extreme, there are even several books with "WebGL" in the title that cover only or 90% of the content Three.js. In the meantime organisations like Mozilla could start and ditch Three.js in favour WebGL. It would be in common interest of everone.