Their system seems to work better for them than our system does for us, so...

One of the ways they keep crime so low. Being convicted destroys your reputation in a country where reputation is extremely important. Everyone loves saying it would be great to have lower crimes like Japan, but very few would really want the system that achieving that requires.

The situation in the US is significantly worse, and probably numerous other countries I haven't experience with. Rather than asking if you've committed a crime, American employers/landlords will do a background check and are liable to turn you down if you've ever been arrested, even if the charges were dropped or you were found not guilty. Comparatively, the reason Japanese employers/landlords may even ask about having committed crime is because they can't find that information on their own freely. This is a fairly ridiculous criticsm, if you ask me. Nobody in any country wants to associate with criminals, often to an unfairly punitive degree, but at least in Japan you are not punished merely for being arrested. And while I don't doubt it happens, it's also far from a universal experience, despite Westerners loving to talk about Japan in broad sweeping generalizations. I have personally never been asked whether I've committed a crime.