Where and how do synonyms and related terms get used?

The taxonomy includes support for related terms (at the vocabulary level) and synonyms (at the term level). Related terms, per the documentation is described as 'allows relationships between terms within this vocabulary. Think of these as see also-references'. Synonyms are described as to be used for variant spellings, acronyms, and other terms that have the same meaning as the added term, but which are not explicitly listed in this thesaurus (i.e. unauthorized terms). The documentation also indicates that these features may not work in all modules.

My question is, where do these work at all? I can envision how they might be useful for clean URLs, for example. I could also see how they might present users with 'see also' links if you were displaying the nodes for a top-level vocabulary (assuming the theme in fact supported this). But I have yet to stumble across such things. Thus, while I'm enticed by working to define such interrelationships in my taxonomy, I can't tell if that's worth doing. Can someone help me understand this better?