The tension is that people want to reuse translations. So maybe you have the story board for the first version. Then, someone makes a new button. In Django, they'd put _("Open ticket") as the text, see there's already a translation, and think they're good to go. Sure, having every page looked at by a translator for every language every time you make a change would be ideal, but also a bit costly and slow. I think there are better options in the middle.