You could swap “Safari” for IE6 and tell the same story. I don’t know what it is about OS dominance that drives such disinterest in upgrading browsers outside of wanting to push native apps for that App Store revenue.
You could also say that Chrome had a huge _interest_ in pushing for browser-alternatives to native Apps because of Chromebooks. Some of that died down once Android support was added. The position on many of these by other browser vendors were that they were harmful for the web. You will likely never see implementations of these non-standard API outside chromium-based browsers.
The other thing which they are very slow to support is new codecs on the video tag. Presumably this is because they want to keep their "video playback" power metrics. the WebKit team is incredibly metrics-driven, which is one reason for their performance and power-efficiency.
