There just isn't enough players to justify it.
Screenshot of a player shooting at another player in Counter-Strike 2.

On October 9th, Valve flat out said that they have no plans for a macOS release of Counter-Strike 2. Part of the reason is because there just weren't enough people playing the game on macOS to warrant continuing support for the platform with their new release.

The unfortunate news was stated plainly in a new Steam Support page for Counter-Strike 2. In addition to dropping support for macOS, Valve is also ditching support for older hardware and 32-bit operating systems.

Counter-Strike 2 represents the largest technical leap in CS history, and our goal is to continue to develop Counter-Strike for years to come.

As technology advances, we have made the difficult decision to discontinue support for older hardware, including DirectX 9 and 32-bit operating systems. Similarly, we will no longer support macOS. Combined, these represented less than one percent of active CS:GO players.

Moving forward, Counter-Strike 2 will exclusively support 64-bit Windows and Linux.​
The flip side to this news is that Valve now made access to a "legacy version" of Counter-Strike: Global Offensive. This will allow people to keep playing Counter-Strike in some form even if they are unable (or unwilling) to move to Counter-Strike 2. You should be able to access the legacy build of CS:GO by right clicking Counter-Strike 2 in your games list, selecting Properties, selecting the Beta tab, and finding the legacy version of CS:GO from the beta dropdown menu.

The issue with the legacy version of CS:GO is the fact that support will end on January 1, 2024. After this date, the legacy release of CS:GO will still be available but certain functionality that relies on the Game Coordinator (e.g., access to inventory) may degrade over time.

Valve is also offering Prime Status Upgrade refunds to macOS users along with those on unsupported hardware. You will have to meet a few special requirements to qualify for the refund though.