I own one of the companies doing it.
The machining doesn't add up to much on the cnc. Each one of those holes takes maybe 7 seconds to cut out. My machine spits out a sheet on average in six minutes cutting out cabinet parts. Those parts took a while, but I had some profiling toolpaths in there too that are slow.
It's amazing how much less stuff gets damaged when it's lighter. A few years ago I started trimming weight out of things when I could, and in some cases even adding handles cut into the parts to make it easier to carry. Sometimes you just build a giant beast and you're f'd through and through....
Its cool how much things have changed with CNC cutting and 3d modelling.
Just yesterday i was showing my project manager how to use a contractor's 3d models to review shop drawings for approval along with the 2d detail drawings.
I regularly ask for IFC files for complex stuff. So much easier/faster to review stuff when you have a model you can orbit through from any angle or section.