> Software teams are capturing a lot of the speedup in the form of more leisure or quasi-leisure time. (To greatly simplify: software teams are offering 2x speedups to their companies. They're then using tools that allow them to work 10x as efficiently, and taking nice long coffee breaks.)

This might be the biggest factor in my opinion. Corporate incentives usually don't reward someone delivering 2x-10x, so an employee who suddenly found a way to multiply their productivity might be keeping that method to themselves and freeing up some time instead.