What is the benefit of macOS dropping support for 32-bit software? It has been hinted at in the past but now we're starting to see solid notice from Apple that it is dropping support for 32-bit macOS programs in the near future. While I can see how this makes sense in the walled garden of iOS, the macOS / OS X environment has always been a bit more flexible in that you could run older software.

We dealt with this when Apple dropped PowerPC and Rosetta, but the change of CPU architecture was a bit more obvious since it was apples-to-oranges. However, the difference here is that our x86_64 platforms can still natively run 32-bit x86 code. It is simply a decision by Apple to cut off 32-bit code. Sure, it is great to get rid of old stuff but it also cuts off useful software which might not be maintained anymore. 

I'm curious what benefit actually comes from dropping support for 32-bit software. Is there any measurable performance gain that we would see from there no longer being support for 32-bit apps running next to 64-bit ones? Or is it simply that Apple doesn't want to maintain the 32-bit APIs and support libraries anymore and this is simply cleaning house?
Apple's explanation for the transition can be found here: 32-bit app compatibility with macOS High Sierra 10.13.4


  All modern Macs include powerful 64-bit processors, and macOS runs advanced 64-bit apps, which can access dramatically more memory and enable faster system performance. The technologies that define today's Mac experience—such as Metal graphics acceleration—work only with 64-bit apps. To ensure that the apps you purchase are as advanced as the Mac you run them on, all future Mac software will eventually be required to be 64-bit.