I am not talking about how hunters should be judged, but how they ARE judged currently.
I happen to agree with you that adding a stride when all other things are equal - jumping form, style, manners, way of going, lead changes - should not be penalized.
However, there's not much question that in both rated shows, and very competitive unrated shows, that's the way it is. And that part of the reason is that it's a clear cut, readily visible way to distinguish one trip from another. If you're in a class with 40 entries, judges are looking for ways to separate the top 20% of the trips. Counting striding and distances makes that a little easier.
This is what the USEF rulebook has to say -
"Hunters over fences are judged on performance and soundness. Judges are looking for great jumping style, quality of both looks and movement, as well as willingness, manners, and suitability of horse and rider. The round over fences itself should be judged on evenness of pace, as well as consistency of distances."
"HU135 Faults .
1. The following faults are scored according to the judges opinion and depending on severity or division, may be considered minor or major faults.
a. Rubbing the jump
b. Swapping leads in a line or in front of a jump
c. Late lead changes
f. Kicking up or out
g. Jumping out of form
h. Jumping off the center line of jump
i. Bucking and/or playing
j. Adding a stride in a line with a related distance
k. Eliminating a stride in a line with a related distance
l. Striking off on a wrong lead on the courtesy circle. (May be corrected with either a simple or flying change of lead)"
Emphasis mine, in both cases. The judge is left with a lot of discretion about how severely to mark the fault, but IT IS a fault, and in a class of 40....