Although pcwalton doesn't agree with me, I believe system languages, based on history of computing, always require a platform for success.
A small example, not all of them became mainstream.
- Burroughs B5500, ESPOL followed by NEWP, nowadays known as Unisys ClearPath
- Xerox Star, Mesa
- UCSD p-System, Pascal
- Constellation OS, Pascal
- Lilith, Modula-2
- Ceres Workstation, Oberon
- Blue Bottle OS (AOS), Active Oberon
- UNIX, C
- Symbian, C++
- BeOS, C++
- NeXT, C and Objective-C
- Windows, C, C++ and .NET
- Mac OS, Object Pascal, C, C++
- OS X, C, Objective-C, Swift
- Android, Java, C++
This is just a tiny sample, I could come up with many more.
This was quite relevant before the widespread of FOSS culture, because we tended to just use/buy the tools of the OS vendor, and most managers wouldn't sign an order to buy yet another expensive compiler just to make some developers happy.
Also languages that aren't first tier on a platform always suffer from integration issues, regarding FFI, tooling with the underlying platform.
Whereas using the OS official languages is just turn the key and go, so to speak.
Rust probably already got its sweet spot with Firefox's adoption and universities that are adopting it for OS classes.
Lets see.