Like so many other applications in the manufacturing sector, it's the long term demand for a product which determines the amount of time, effort and money which gets thrown at it.
In the situation of the Defiance MX, it could very well be that the demand or really the lack thereof which is compromising the forward movement. Far too many of us believe that we as individuals are the key guiding the demands when it's the major demands of thousands which drive the potential product development.
The other practical problem is time and money to devote to the development of new designs. When the regular production lines are full or nearly so, the drive to add to what's already full is far lower without adding new capacity to existing capacity. That costs money and trying to predict profits over expense can be daunting. Simple but true.
My guess is that the magazine manufacturers have their hands full producing for the daily consumption already. The trick is how to work in a new design while maintaining the current production numbers needed for the profits.