Thermals are indeed a good reason too. While it seems that the current MB Pro does a reasonable job with cooling the CPU, it is obvious that with better cooling

Thermals are indeed a good reason too. While it seems that the current MB Pro does a reasonable job with cooling the CPU, it is obvious that with better cooling you could drive the CPU harder. As the laptop is for me a mobile workstation, there is also the point that I would prefer a slightly bigger laptop that runs faster. Which is why Apple should differentiate between the "air" and the "pro" line more. There would be a place for a 15" air, which is a slightly thinned version of the current 15" pro, and a true pro machine which sacrifices a bit of portability for features and performance. My current dream machine would be roughly like the late 2015 MB Pro (that happens to be the machine I am typing this on), with at least a 16" screen (the bezels are plenty large on mine) and 1-2mm more thickness, allowing for good thermals and more serviceable parts. For a pro machine a battery, keyboard or ssd exchange needs to be doable by a skilled technician on-site.