Need use cases for entities

Can anyone explain, why those huge list of entities is needed in real world? I’ve seen those only for HTML escaping & copyright sign.

I’d like to ship simplified decoder for browser build. Or, may be, just reduced list of current HTML5 set (generated from DOM decoder result vary on document type. Manualy reduced list not vary, but support much less entities than DOM.

Does it worth to spend time for light builds, or you know examples, when rare entities are used?