Having these features in the standard gives browsers and transpilers a common, well-specified target to work towards. If you only need to support a subset of b

Having these features in the standard gives browsers and transpilers a common, well-specified target to work towards. If you only need to support a subset of browsers you can turn off compilation/polyfills for specific features, which sometimes leads to better performance and smaller bundles. I think of it like TypeScript and Babel running ahead experimenting with new ideas, ES following along turning the good ideas into a spec, and browsers taking up the rear implementing the spec. It’s a pretty decent system.