Eventide can answer better than I. The reasoning often given is that the curve is ‘skewed’ to allow finer access to the more important or useful values. I can see that, in many cases. There are also wider ‘dead spots’ around some normally centered parameters, like pitch/delay mixes and such.
When it becomes more problematic for me is where a pitch value won’t re-center perfectly. Or an envelope parameter hits -1 to +1, but not 0 with any MIDI CC value.
I also understand that some parameters might only have 3 values, and others a few hundred. So compromises have to be made in compressing / expanding to 128 discrete values.
