Yes, I get that Jane and Joan are fictional and that your story is real. Perhaps I didn't state things clearly so I'll try again:
If you'll allow me to propose a hypothetical: let's say you did have recurring painful merges because (borrowing from the fictional story) someone was continually adding new features while someone else was continually tweaking error messages such that there were many conflicts which needed resolving upon every code check-in. You likely would have put the error messages into resource files much sooner and avoided these recurring painful merges. But because you didn't have this hypothetical situation (it ain't broke, thus you didn't fix it) it made sense to push the pain of localization off to when it was actually needed.
If you'll allow me to propose a hypothetical: let's say you did have recurring painful merges because (borrowing from the fictional story) someone was continually adding new features while someone else was continually tweaking error messages such that there were many conflicts which needed resolving upon every code check-in. You likely would have put the error messages into resource files much sooner and avoided these recurring painful merges. But because you didn't have this hypothetical situation (it ain't broke, thus you didn't fix it) it made sense to push the pain of localization off to when it was actually needed.