Your app probably works great in the region and language your developers are based in. But switch to Germany and suddenly dates are formatted wrong. Switch to Arabic and your layout breaks. Launch in Japan and a string that fits perfectly in English is now truncated into gibberish.

Localization bugs are embarrassing, easy to miss, and completely avoidable. 

Now you can configure the OS's region settings and catch bugs that your local developers and testers are likely to miss. Localization testing is good practice whether you're expanding into new markets, maintaining compliance across regions, or just want your Berliners to be happy.