Because there's now less time to add new features, ECMAScript 2016 features a smaller number of features when compared to the mammoth, ground-breaking, and awaited ECMAScript 2015 (ES6) release.
The release has limited new features due to the new philosophy of providing smaller, more frequent updates
From now on, expect smaller changelogs from the ECMAScript team, since this was the plan set out last year. Fewer breaking changes means more time to migrate code, instead of having to rewrite entire applications, as developers did when ES6 came out last year.
The upcoming Chrome 52 release will feature full ECMAScript 2016 support, while Firefox added ES2016 features across dfferent versions.