> some UI-level APIs This assumes that there is agreement on what the UI experience should be. Navigation patterns, menu bars, keyboard shortcuts, touch gestur

> some UI-level APIs This assumes that there is agreement on what the UI experience should be. Navigation patterns, menu bars, keyboard shortcuts, touch gestures.. But there is still active competition between OS vendors on UI. Just in the last decade, the most common form of interaction with a computer has changed from mouse and keyboard to touch and speech recognition. > It's easier for me to cross-compile C to JS than to compile C on all the different platforms I use. What happened? The web is a lowest common denominator. A web app is still missing a lot of affordances that users take for granted in a native app on their given OS. That is why still in 2019, there are new native iOS and Android apps being developed. Look, there are even entirely new programming languages being invented (Swift) or integrated (Kotlin) for the purpose of writing native apps for those platforms. Specifically regarding compile C, I don't see what your problem is compiling C. You can even compile C11 on windows with Clang. Yes you may choose to include a OS-specific header and it won't compile, but also your JS doesn't necessarily run if you call some browser specific function.