[Yoric]

Many of these components have been made part of the ecosystem long after they were introduced in Firefox. Also, the more platform-specific you go for each component, the more you're going to introduce subtle incompatibilities between Firefox running on different versions of Windows or in Firefox for Windows vs. macOS vs. Linux. Also, for a very, very long time, Microsoft had an extremely poor record in terms of security fixes. So what happens when you rely on a Microsoft http library and Microsoft takes a year or two to release a 0-day?

There are benefits to this approach, of course, but the costs would have been consequential.