Why doesn't C?
Since C++ lib's binaries are mostly platform dependent, the best way to get them is to compile from source or publish the compiled binaries to the platform's (ie the OS) distribution repos. As such you will find almost all C++ libraries on apt repo (on debian) as deb archives, as rpm on red hat/fedora distros. If the binaries are not readily available, they can be compiled (or are automatically compiled if the repository app can do so - like fink does for Mac OS X).