Because the same also applies to clang, and contrary to what people think, Apple like every other big tech, is only as nice to FOSS as they need to be for their own purposes.
Same applies to all C and C++ compiler vendors, that have replaced their proprietary compilers (there are plenty more than just clang/gcc/msvc), with LLVM.
Such is the freedom of Apache/MIT/BSD style licenses.
Parent was not complaining. Parent was asking what the rationale is behind maintaining a separate LLVM fork instead of upstreaming and reducing the maintenance burden on Apple engineers.
I would not say its about niceness, its more about necessities. If ya don't own something, the walls are high to have anything changed, naturally. Because it might not be aligned with what the owner has had in it's mind. And you want to move quickly. So you fork and apply your changes.
But i also think, in the long run, it hurts, bcs at some point, you forks are too diverged. But so is life.
Because Apple does not direct the LLVM project, and they have their own corporate designs and plans. I'm sure they upstream what changes they think will be accepted, but there's no guarantee upstream would accept what they want or need let alone on the timeline they need it.
