The development of western scales (or for that matter the study of all scales western or eastern) is a fascinating topic. The study of tuning or temperament also is a very interesting subject. Probably the earliest scales that are known (although I don't know the exact historical facts in this regard) are the scales of the Greeks. The Greek culture had a great love for ratios be they in relation to the motion of planets or the sound of the Greek lyre. From the Greek scales or modes as they are called, the western scales developed and settled on only two modes (major and minor). Jazz music and other forms of music do make use of other modes and scales.
While there are also other scale temperaments which have a lot to do with ratios (a more complex topic than one might think), the western scale is now usually what is called equal tempered.
Here is a brief introduction to this complex topic:
The concept of equal temperament is that is not key dependent so each half tone step is equally distanced mathematically.
The concept of dividing scales equally I believe to be more of a product of a kind of scientific bias of the western mind than anything else probably derived from the quantization of all things introduced to western thought by Descartes. (sorry, my philosophical background is showing :))
Bottom line however and a question: Why do all instruments have to have equally spaced intervals? Truth is they don't and music is more about ratios than it is about the placement of notes. So when we speak about an instrument like the Eigenharp which has a flexible way of assigning notes to keys, different arrangements simply reflect different relationships. I guess in many ways I am not that tied to a western equal tempered bias or feel that all divisions have to be equal distance in terms of frequency.
Certainly, the Eigenharp has got people thinking in new ways as the Tenori-on has done for thinking about sequencing. What is clear is that the idea of a fixed way to play music is changing and as I have stated before, I think that's a good thing. Are there going to be pitfalls along the way? Sure, but those are the very stuff of good music because you never know where they will lead.