Unfortunely did not come with an OS, wasn't freely available, and quite costly.
Remeber that until AT&T was allowed to take commercial advantage of UNIX, its source code was available for a symbolic price, and it came with a C compiler toolchain, at least until Sun started the trend among UNIX vendors of spliting UNIX development tools into an additional purchase.
The UNIX vendors that had Ada compilers, that was an additional purchase on top of UNIX SDK (which already had C and C++), so unless there was a hard requirement to use Ada, no one bothered to pay extra.
Indeed. Ada killed itself, partially because it was one of the DoD approved languages and so the vendors got on board with raping and pillaging everything they could, killing the whole thing in the process.
I keep using "mostly safe languages" as kind of abstract term, Rust comes into speech even in scenarios where other alternatives would be a viable option.
