A big font with thousands of characters might occasionally have error on them, that’s why someone have to maintain them and checking for all visibility test. This even true for any CJK languages.
Whenever they add new symbols to Unicode, for a start.
Probably other reasons too, on occasion. For non-Latin languages with thousands of characters, I’d imagine certain unusual combinations occasionally get discovered that need rendering tweaks? Things like that.
Why would a font need updating?
A big font with thousands of characters might occasionally have error on them, that’s why someone have to maintain them and checking for all visibility test. This even true for any CJK languages.
Example of error on Google Japanese Noto font: https://github.com/notofonts/noto-cjk/issues/286
Whenever they add new symbols to Unicode, for a start.
Probably other reasons too, on occasion. For non-Latin languages with thousands of characters, I’d imagine certain unusual combinations occasionally get discovered that need rendering tweaks? Things like that.