Today I've learnt that in Unicode there's a separate block for katakana letters enclosed in a circle - all of them, apart from ン. Then I've realised that the logo of this particular stack is a letter in circle as well
My question would be: What is the actual usage of such symbols which is that important that encircled kanas are introduced to Unicode and why nevertheless, an ン is not a thing.
There's a similar question about kanji however it does not cover katakana.