much like libc, isn’t it? Apple writes tons of their own software in Swift and the number keeps going up. They’re trying to move more and more of the system to. It’s going to be loaded and in every system whether a user uses it or not.
No different from the objective-C runtime.
On Windows the equivalent would be MSVCRT which is sometimes shipped with the OS and sometimes not (depending on the versions involved). Sometimes you even need to worry about the CRT dependency with higher level languages because their “standard librairies” depend on the CRT.
So if you see that being installed with Java or C# or Unity, now you know why.
Also unixes let the sysadmin install additional libraries. How do I `apt install libswift2` on an iPhone?