The keyboard size that became the current standard dates back to the 1880s when pianos became bigger to suit large performance venues and a keyboard of this size was acceptable to large-handed European male virtuosos such as Anton Rubinstein.  (See Keyboard history). There is nothing ‘sacred’ about today’s conventional size.
Pianists with smaller hands – women, children and people of Asian descent – were not considered. If the manufacturers were designing the piano today, one would expect that they would conduct careful studies of hand spans across the human population and relate this data to the demands of the piano repertoire. If only one size could be provided it would be most likely be close to the DS6.0.
The basic premise of ergonomics is to adapt tools to humans, not the other way around.
What we have is a piano keyboard which is too small for practically no-one, but too big for many.  It can be compared with ski manufacturers only providing a size based on the what suited the first male skiers in Switzerland, and expecting everyone to use that size.
Sometimes people say that there has been no demand for change. But people rarely express demand for innovation before they have experienced a new product. One only has to consider the constant innovation in the IT industry – anticipating what consumers may like, testing alternatives and then creating the demand. For nearly everyone on the planet, they have only ever seen and experienced one piano keyboard size in their lives, so have difficulty imagining the implications of a different size.