It's about protecting German workers' safety, not just "German jobs". They're inseparable goals. One abused worker is a threat to all workers.

Anyway yeah, realistically, the reason rich-world workers should care about poor-world worker safety is because it's in their material interests: They will be forced to do unsafe things at work, or else face being fired/laid off and the company will move the work to locales where (expensive) worker safety isn't done.