are somewhat limited in size by the size of standard parts which has not changed since early wrist watches of 30mm cases. From there the goal was to go thin over the years and increase the power reserves beyond 24 hours. All this resulted in standardized parts which carry certain known loads and use only so much energy. If you look at any watch company and note the size of the movements there are mostly 27 to 31mm in size yet they are cased in 40mm plus cases with lots of dead space, in and out. Its not just PP. To increase the size of the movements means greater thickness, larger parts, shorter power reserves and accuracy compromises from increased ratios between the larger heavier parts. In addition, the whole factory would have to be retooled to make the new parts. The technology with the new silicon parts may make the task of making larger movements less expensive and less daunting, but I think the companies are quietly betting large watches are a fad which will pass.