Apple dropped support for 32-bit applications on iOS quite some time ago, but it looks like 32-bit support is also coming to an end on macOS soon.
Starting with macOS 10.13.4, Mac users will receive a one-time alert when attempting to run a 32-bit app. The notice will read that the app is “not optimised” for Apple's platform, but it will still run. Apple has warned developers that macOS High Sierra will be the last version to support 32-bit at all. At this point, Apple no longer accepts any 32-bit apps on the Mac App Store.
So for now, it looks like existing 32-bit apps will continue to run on macOS. However, when the successor to High Sierra begins rolling out later this year, 32-bit apps will no longer run and eventually, they may even be wiped from the Mac App Store.
The tech and games industries have been moving away from 32-bit for years now. Recently we even saw Nvidia drop 32-bit support for its GeForce graphics drivers. We'll likely see more companies follow this same trend over the next year or so.
KitGuru Says: Most PC and Mac owners will be running 64-bit capable hardware at this point anyway. However, the software world may need to catch up in some limited areas as more companies drop 32-bit support.