Changing the .TH case convention throughout the Unix world is about as futile an effort as English spelling reform. Doing it for groff-related man pages only would simply brand groff as quirky.
At least the current convention has the virtue of simplicity. A convention of matching the case of commands or functions needs extra rules to settle how to render titles like INTRO(1), EXEC(3), STRING(3), or various stuff in man7. As for the history, Dennis's original man-page template was generally deemed worthy. The only discussions I remember were about the overall division into sections and how to organize pages within a section. The overall division turned out to be a little squishy, witness the aimless evolution of the remits of sections 5-7. I am happy to note that the organization within section--intro plus alphabetic--has held firm. (My most substantive contribution to the v1 manual was holding out for alphabetization versus a topical outline. My main talking point was the inutility of topical organization in the 15th edition of Encyclopaedia Britannica.) Doug
