“Evergreen” Does Not Mean Immediately Available
With the actual, final, no-seriously-we-mean-it-this-time death of Internet Explorer, evergreen browsers are now the main consideration for desktop and laptop browsers. This is great! It means we can spend a lot less time fretting about who can use what.
Spending less time does not mean spending no time, however.
Chrome and Firefox are updated every few weeks now, but it doesn't mean users apply these updates really fast.
And well, Internet Explorer is not so dead yet anyway… so keep using progressive enhancement, and you'll be safe!