I can only speak for the UK, and there, I guess you would have to go back to a time (before my time) when competitive riders started using sprints and tubs imported from continental Europe. As far as I know, the 700c HP rim is the same size as those, in as much as you could change between sprints and 700c HP wheels without moving your brake-blocks in their slots.
The original faux sprint/tub combination of Mavic Module 'E'/Michelin Elan dates from about 1975- probably took a few years to catch on. IIRC before that, in the UK, unless you were using sprints/tubs, the narrowest option was 27"x1 1/4", so, for anything other than racing, that remained the standard into the '80s, especially on mass produced bikes.