For almost all platforms that's true, but the culture of standardization on the Web is unique. It comes from wanting a Web page to have the maximal chance of running across all standard-compliant browsers, forever - that's just not the case for practically every other platform.

If only that was true. Javascript has had all plenty of inconsistent behaviors across browsers and the feature matrix for what is and isn't supported in each browser is hugely complex. And even if that was true standardizing the results of malloc makes no sense, it gives you no extra compatibility guarantees for any sane programs and no one cares about insane ones.

I've yet to see a standard-conforming C app that relied solely on the standard library - which, of course, includes malloc/free - to not run across all platforms (that have a filesystem and a console, or some equivalent input/output facilities, anyway).