1. Singletonish things like global allocators, rayon-core, etc
2. You may have made a package static safe to mutate with a mutex, but it could be a bad thing to have different versions of that mutex.
3. Compile time computed tables (unicode table, perfect hashes, etc) could be imported multiple times ballooning the binary.
4. ABI/type compatibility with any reexported types
1. Singletonish things like global allocators, rayon-core, etc
2. You may have made a package static safe to mutate with a mutex, but it could be a bad thing to have different versions of that mutex.
3. Compile time computed tables (unicode table, perfect hashes, etc) could be imported multiple times ballooning the binary.
4. ABI/type compatibility with any reexported types