Well, the market itself DEMANDS action from the manufacturers. The will of the customer, if the basic premise of supply and demand is true, basically says that whatever the majority want, the majority get... They simply get it faster if they are vocal about it.

Look at how Yamaha responded to Roland in the eighties (or early nineties)... Roland were ahead, and Yamaha users DEMANDED (whether tacitly or vocally) that they catch up and surpass them, or wither on the vine.
Yamaha responded.
Korg owners DEMANDED (whether tacitly or vocally) that Korg develop something the equivalent of SA voicing, or users would move to what DID have the feature...
Korg responded.
These guys do their market research. If they read enough about how the majority of arranger power users want better MIDI capability, that is a powerful voice for them to ignore at their peril. The first guy that implements it has a definite advantage. As Yamaha DID with SA. Now Korg have nearly caught up (just waiting for the samples). Did anyone DEMAND it from Korg, or did they simple FEEL the demand? That's splitting hairs.
But personally, when NO-ONE has a particular feature (like user definable arranger codes), if enough users that WOULD like it were vocal on the issue, that's a demand that no arranger manufacturer would ignore. Not if they wanted to get a leg up on the competition, anyway...

What astounds me is the thought that it MIGHT not happen, yet is simply code, and fairly easy to implement code at that. We aren't talking SA technology, or Guitar Modes, this is MIDI 101...
And if the manufacturers, after seeing what happened in the eighties when MIDI was first introduced, and an explosion of synth buying happened because FINALLY we could control two keyboards from the one can't see that exactly the same thing would happen in the arranger world IF they could talk to each other, then capitalism is a fiction..

The goal is to sell as many units as possible. If a feature that would enable that to happen is ignored, the market itself DEMANDS they implement it.
I just happen to feel that we COULD help it along, by telling them that IF they implemented it, we WOULD buy a secondary arranger.
I have completely given up on expecting Roland's best features to be implemented in a Yamaha, and Yamaha's best implemented in a Roland. But if I could link the two and they work as one. I GUARANTEE I would be buying a Yamaha to go along with the Roland.
Heck, if the codes for the arranger WERE standardized, we might actually see the return of the arranger module, because it could be made a LOT cheaper if it weren't for the need to duplicate almost ALL the controls from the keyboard version. I have no idea why anyone expects a module version of a TOTL arranger to be much less expensive than the full version... the only thing it drops is the keyboard and the slightly larger case. All the electronics are still exactly the same, buttons, sliders, knobs, etc.. But if the MIDI codes were comprehensive, it wouldn't need anything much more than a power button and a volume knob! That's a HUGE saving, right there...
But unless we talk about it, unless we make our desires known, there's no DEMAND for it, and probably no action.
It's up to us. Korg users got SA technology. We could get this too, if we want it bad enough. Aren't we TIRED of always having to make SOME kind of compromise between arrangers? Wouldn't we rather have two (two MOTL would probably do!) and have NO compromise?
I know I would...