I'm not Korean but my understanding is they do use the Chinese-derived script occasionally, for emphasis or to solve ambiguity, among other things. So some users will need access to that script too.
My very limited understanding is that Hanja use is extremely rare today, only ever cropping up in niches of academia. Basically everyone will exclusively use Hangul and will disambiguate with synonyms, idioms, etc. instead of Hanja.
Yes from what I heard it would be very few users, definitely not the general public. Maybe academia, signage, marketing, historical/legal use, etc. It might be enough to simply plug the gap with occasional images instead of fonts. But CJK fonts often do apparently include Hanja.
https://en.wikipedia.org/wiki/Hanja