To build software, one often just has to press a button and minutes (or maximum hours) later, the ready to test software has been build. This makes it easy to do this often. For hardware, when things get physical, this takes more time. When lucky, you can produce something in minutes or hours, like a 3D printing part, but often it requires production preparation, production, external part delivery, assemble, transport, which all take time. And the worst, because we are so driven by efficiency, lead times that exceed actual time needed by far. For instance, production takes 2 hours, but for planning and other reasons it takes a week or 2 to actually get it. That is, talking about efficiency, at best a 2.5% time efficiency.