Hepburn may not be an ideal match for German, but it's still a better one than Kunrei-shiki. I'm fairly sure there is no language in the world whose pronunciation of Latin letters matches the latter (hah!).
The only thing Kunrei-shiki has going for it is that it's more regular and can be more easily matched to kana. It's easier for Japanese kids to learn. But they are not the ones who are going to use it primarily.
You could use different romanization systems for each foreign language, and there are some (there is one for German where あいち is "Aitschi"), but that doesn't end up serving anyone well in a globalized world with an Internet.
Hepburn may not be an ideal match for German, but it's still a better one than Kunrei-shiki. I'm fairly sure there is no language in the world whose pronunciation of Latin letters matches the latter (hah!).
The only thing Kunrei-shiki has going for it is that it's more regular and can be more easily matched to kana. It's easier for Japanese kids to learn. But they are not the ones who are going to use it primarily.
You could use different romanization systems for each foreign language, and there are some (there is one for German where あいち is "Aitschi"), but that doesn't end up serving anyone well in a globalized world with an Internet.