Just because your site is fast and functional in the top five browsers in the West, doesn't mean it'll load the same way worldwide. Other regions have different names filling their pantheon of top browsers, and it might be worth a little bit of effort to make sure you're presenting well there, too.
As Peter O'Shaughnessy notes on Medium, we can all get a little caught up in our Western bubble. When widen your range to worldwide, Chinese app UC Browser steps into third place. In Russia, Yandex is in 2nd place. And in Africa, Opera Mini has 58% market share.
It's also important to know that when looking at stats, sometimes Chrome isn't Chrome. Samsung Internet, which is based on Chromium, sometimes shows up as Chrome. Especially if you're using - surprise, surprise - Google Analytics.
I'd also add that it's worthwhile jumping onto older hardware, just to make sure everything loads snappily. It might be good to experience the extra second or so it takes someone else to load your page; maybe it'll inspire you to cut the fat for the benefit of those not blessed with the latest machines.
You may or may not care how many readers in Russia can easily access your content, or if your site is readable in China. But O'Shaughnessy quotes marketing expert Bruce Lawson very well here: "Where will your next customers come from?” You don’t know. In our truly worldwide web, you can’t know."
[Via Peter O'Shaughnessy]