Different products/teams can move at different speeds if they target a specific market. For example, for internal apps teams can expect that browsers are up-to-

Different products/teams can move at different speeds if they target a specific market. For example, for internal apps teams can expect that browsers are up-to-date, or that even only a specific browser will ever run the app. Also, people who write JS for back-end (eg node.js) or an embedded engine can control the environment their code runs in, and can use more up-to-date features. It’s similar to all the new tweaks and elements in HTML or DOM. If you’re working on Wikipedia, you will likely never get to use them. But if you work on a more niche app, they become quite useful. Over time, old browsers die out, and the amount of people who can use new features expands; early adopters do the testing for the late majority.