Not "magically", but more reasonably and without forcing your entire program into a different state, breaking any ability for libraries to work with a huge rang

Not "magically", but more reasonably and without forcing your entire program into a different state, breaking any ability for libraries to work with a huge range of functionality consistently. C locale handling is basically impossible to work with robustly, even before you get into how it can't be effectively used at all in a thread safe way.