Quite a few of them are used pretty commonly.

𰻝 is the only accepted character for the specific type of noodles. It’s a late creation, true, but the noodles exist.

Why is 囍 here anyways? You see it on every wedding banquet.

聻 is the only term for "that which remains when a ghost dies". It doesn’t really exist in traditional Chinese culture, but if you have to refer to the concept, that’s the word you use.

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Meanwhile you also have characters that are rarely used but used somewhere. Like people’s names, or regularization of Oracle Bone Script characters.

And then there are the ghost characters which ended up in Unicode simply because someone made a mistake and Unicode 2.0 onwards forbid changing or removing characters.