> ABI stability for the standard library is motivated by large, old, coroporate codebases which had poor API practices, passed STL types across ABI boundaries, and subsequently lost access to the source code of those libraries and applications or otherwise cannot recompile them for some reason. Many people question the wisdom of catering to such users.

It's also motivated by Linux distributions and other complex systems where rebuilding and installing the world in one go is not possible/feasible.