Part of my point was: if these dependencies are still maintained, chances are their API remained stable, so you only have to compile it with the new headers in

Part of my point was: if these dependencies are still maintained, chances are their API remained stable, so you only have to compile it with the new headers in most cases. Sometimes, you indeed have to compile obscure dependencies. This is a consequence of a userspace where most software is open source, and where distributions systematically recompile every package. As a side-effect, it is also generally more portable across architectures.