So why don't triple walleys ... count for something. ...
Or this version of a double axel - forward right inside edge, (instead of forward left outside edge), rotate 2.5x, land on right back outside edge.
Is it physics, tradition, the whims of the ISU?
For those jumps, walley and inside axel, I'd say it's primarily a combination of physics and tradition.
They can't be done as triple jumps. Only exceptional jumpers can do them as doubles.
By the 1970s (early for men, late for women), triple jumps were defacto required to win championships and then became required to compete in senior short programs at all.
So the best jumpers were trying to do all the triples, including triple axels, and quads. And triple-triple combinations. That became the way to show off one's jumping ability.
The pretty-good jumpers were just training to do all the triples. The so-so jumpers were just trying to be able to land
some triples.
There wasn't a lot of incentive for the best jumpers to train an unusual double jump, or for the OK jumpers to spend training time and performance stamina on unusual singles. So even the singles from these takeoffs remained relatively rare, and doubles practically unheard of.
Then along came the IJS. Evidently it never occurred to the designers to include these jumps into the Scale of Values. Perhaps they didn't think they were even possible as doubles. And because fairness meant limiting the number of jump slots available in long programs, they didn't want junior and senior skaters to be penalized for doing singles from these takeoffs. So they left them as "nonlisted" jumps that count as transitions, gain no points, and don't waste jump slots.
That you could call the whim of the ISU officials who designed the new scoring system. But it wasn't a whim to eliminate something that skaters had already been doing. At worst it was a failure to imagine the possibility that some exceptional jumpers in the future could master double jumps from these takeoffs and to build in a reward for doing so.
Suppose we imagine it. How much do we think double walley or double inside axel should be worth? Maybe we should ask any elite skaters out there whether they've ever tried them and how they think the difficulty compares to the standard double and triple jumps.
I think both those jumps as doubles should be worth more than double axel, and probably more than triple salchow. But I"m sure there would be room for tinkering with the value once skaters start trying them.
Then if doubles eventually became . . . well, probably not common, but no longer incredibly rare, then it might be time to start thinking about
For single jumps, and that includes not only single walley and single inside axel, but also variants of other single jumps from normal takeoffs, such as back inside landings or split, tuck, hitch-kick air positions, what would be the best way to allow skaters to use these jumps as transitional moves without wasting jump slots on single jumps? Allow them to earn more points than the current +3 GOE for single jumps? Allow them not to use up jump slots if they're obviously intentional singles?
If we want more variety in long programs, there need to be more options in the rules to give incentives to use these jumps.