> Shaves seconds off the time it takes you to write an address?

More like minutes. Address input in Japan is a colossal pain in the ass. You have some sites that only allow half-width characters (e.g., ｷﾀ), some that only allow full width (キタ), some that require you to write your address twice and once in romaji, which can be half width (kita) or full width (ｋｉｔａ), some require you to write it in hiragana instead, sometimes numbers need to be full width(123 vs １２３), sometimes addresses have random unicode symbols like ・or Ⅲ (yes, Roman numerals are common in addresses) or ⑧ which may or may not be recognized, and more. There's no standardization in addresses at all and no street names, so every building gets some bizarre-ass name unique to it and the names sound like the title of a JRPG. You might even get stuff like 〜ＴＨＥﾋﾞｯｸﾞPALACEモナコ：Dréam Ⅱ〜

And the fun thing: every site has its own input standards, and no, they don't tell you what the error was. Most simply say "You can't submit. There's something wrong on this page." Some let you hit the send button, fail, and make you input everything all over again.

Having a code to input an address saves users loads of time and stress, assuming web developers implement it.