The point of the LGPL is that it allows static or dynamic linking with proprietary software, but it requires that users be able to modify the LGPL part and relink it with the proprietary part and have the result work, as long as the modified part is compatible with the proprietary part. With dynamic linking thats simple, just drop in a new LGPL library, but with static linking you have to share the .o files for the proprietary software to enable user relinking.