Apple actually sort of does have a backend framework: WebObjects. They just seem to have deprecated it in favor of other solutions. Still, I've noticed at least iTunes Connect is still using it. And for what it's worth, Swift is going to have more server related stuff coming to the standard library (https://swift.org/server-apis/), and I wouldn't be surprised if Apple starts adopting this eventually as well as it continues to improve.
I'd add ReasonML to the Facebook list - one of the most promising general purpose languages out there, IMO.
You could add Folly as Facebook's backend C++ framework (it's somewhat analogous to Google's Guava for Java).
Apple: LLVM (I know I’m stretching the definition here :) ); Objective-C, Swift; N/A; Cocoa.
Microsoft: .NET CLR; Visual Basic, C#, F#; ASP.NET; N/A.
Facebook: HHVM; Hack; N/A; React.
Google: Go, Dart; Golang, Dartlang; GWT, Guava; Angular; Android, Flutter.
Oracle: JVM; Java; APEX; N/A.
It seems that for some reason just Amazon doesn’t want to play :)