If we look at caniuse.com, we can see that some browsers still do not have support for ES6. Why don’t all the latest browser versions support ES6?
One main reason for this is that the browsers that still do not support ES6 are not as popular and used as the other browsers. Because they are not as used, the developers might think that it is not worth all the time and effort to implement ES6 support to them as they are being phased out or overtaken by competitor or alternative browsers. For example, the Edge browser, which supports ES6, is replacing Internet Explorer, which does not support ES6.