I hike on the Continent, where everything is tabulated in hours, not "milage" (kilometrage?). Theoretically this makes some sense, and despite different hiking paces, within certain regions the systems _can_ be consistent aids.
But each region has it's pace. I live near the Vosges, and in these lower mountains, the Club Vosgien maintains the signage, and they walk a little slower than most. In the Swiss Alps, on the other hand, "one walks quickly," as a friend said. I'm more of a Swiss hiker---but even then, if I were to time myself, I would have to stop the stopwatch every time I stopped to take a picture, retie my shoe, visit the bushes, etc. to maintain the pace.
If done consistently, subjective scales like "hours" can be very helpful. I'm sure one can use the elevation profiles of computer mapping to calculate pace vs/ work; but I bet such a scientific approach would just about reflect the experience of the masses. No scale I've run into can quite accurately predict how often I'll want to stop, marvel, snap pictures, soak the feat, etc. The Swiss are a bit too quick for this, I think.