MacOS has supported 32-bit apps and 64-bit apps for years. I don’t know why Apple has decided to drop support for 32-bit apps.
I still use Photoshop CS6 because I never signed up to the subscription model so if I upgrade to Catalina I won’t have Photoshop anymore (unless I run it in a VM).
This is the first version of macOS that doesn't support 32-bit applications. Most of the software in question hasn't been updated in years so people are hesitant to upgrade. It's mostly a legacy issue.
In Catalina, Apple dropped 32 bit support. And in the same process dropped a lot of Frameworks that had been deprecated for ages. 64 bit software that didn't rely on deprecated Frameworks continue to function
The last released Macs that were not 64-bit use Intel Core Solo or Intel Core Duo processors, and those haven't been able to upgrade past Mac OS X 10.6 Snow Leopard, released over a decade ago in 2009. According to Apple's definitions of "vintage" and "obsolete", this puts these Macs well into the "obsolete" category.
The upside to removing 32-bit is shrinking the size of the system, removing complexity, shrinking the testing matrix when modifying system frameworks, etc.
The writing has been on the wall for 32-bit apps for a long time, including warning users when launching a 32-bit app that it would cease working, and showing users a list of incompatible software when upgrading to Catalina. App developers were incentivized to release updates to their apps (using 64-bit toolchains that have been available since 2007 and before), and users were given warnings about upgrading if they need 32-bit compatibility.
Meanwhile, over the past decade there has been significant improvement in virtualization technologies, which allow you to run 32-bit operating systems with great performance. You can run Windows XP in a VM or WINE in a Docker container (which runs inside a Linux VM on macOS).
32-bit app support has been removed. I'm guessing this will allow them to remove 32-bit support from future processors. It might already be gone in the A11 chip.
High Sierra will be the last version of macOS to support 32-bit apps, so this same transition will happen next year on the desktop.
Apple literally removed chunks of the processor that was needed to run 32 bit software to make room for more forward looking features.
Backwards compatibility would mean that MacOS should still have support for 32 bit apps? PPC apps? 68K apps? Should they have ported Carbon to 64 bits? Should they have kept support for QuickDraw from the 80s? QuickDraw GX from the 90s?
Adobe's CS products were 64-bit only on Windows for a while as well, due to Apple's last minute decision to drop 64-bit support for Carbon and force developers into Cocoa use for 64-bit apps. While Adobe addressed the situation with CS5, not every company out there has the same resources available for such a rewrite of their Mac-specific layer on multiplatform software.
tl;dr -- Apple is at least partially to blame for the slow move to 64-bit apps on the Mac platform.
I believe the main reason Apple wanted to drop support for 32-bit apps is so they no longer have to support the Objective-C 1.0 runtime, which must’ve been requiring more work to maintain than they wanted to invest.
I'm still mad about Apple killing 32bit support; I don't have a few extra grand a year to drop on Photoshop. If they drop x86 support, too, I might finally jump ship.
Apple dropped support for 32-bit applications. That's different from requiring 64-bit applications to stop abusing unused address bits—something that hasn't ever been commonplace for x86-64.
Heads up for developers like me building Mac apps, this release is going to take a little more adoption time than most due to the 64bit-only nature of this release.
For example, I know there is a contingent of people who are stuck at Adobe CS6, whose certain critical components are 32 bit. Since Adobe no longer sells permanent licenses, opting to only rent their software instead, it's impossible to get these updated. And these expensive and still-in-use licenses are going to die the moment people update to Catalina.
I still use Photoshop CS6 because I never signed up to the subscription model so if I upgrade to Catalina I won’t have Photoshop anymore (unless I run it in a VM).
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