> The original SGML specification is in front of my eyes right now and  

I suspect that you don't actually mean the SGML specification, but rather
the DTD for one of the W3C languages.  Not having paid for the real SGML
specification, I don't know if it says much about intended uses, but
my perception is that the typical intended use was for things like
Electronic Data Interchange, where the detailed structure of a business
document, like an invoice or bill of lading, would be marked up, 
or for documents to be placed into an indexing system, where it would be
important to identify things like addresses.

What I've seen as typical examples of roles, many of which actually 
represent primary structure, like navigation bars, are things that
would need to marked by elements in the above sorts of SGML 
applications.  It's actually things like strong/bold that wouldn't -
in fact, in EDI, I doubt they would have any presence at all.