Comment by ordu

I don't know, but I have a guess. Someone didn't want to deal with unsafety of dealing with memory allocated in C code. Serialize/deserialize makes it easy, no need for unsafe, no need to learn all the quirks of the C-library allocating the memory.

I had experience with writing safe bindings to structures created in C library, and it is a real pain. You spend a lot of times reverse engineering C code to get an idea of the intent of those who had wrote the code. You need to know which pointers can address the same memory. You need to know which pointers can be NULL or just plain invalid. You need to know which pointers you get from C code or pass to it along with ownership, and which are just borrowed. It maybe (and often is) unclear from the documentation, so you are going to read a lot of C code, trying to guess what the authors were thinking when writing it. Generating hypotheses about the library behavior (like 'library never does THIS with the pointer') and trying to prove them by finding all the code dealing with the pointer.

It can be easy in easy situations, or it can be really tricky and time consuming. So it can make sense to just insert serialization/deserialization to avoid dealing with C code.