Every Mac transitions to ARM, only a very small amount of Windows PCs are running ARM. SO right now there's not an large user base to incentivise software to be written for it.
So if you support macOS/x86, macos/ARM, and Windows/x86, then the additional work to add Windows/ARM is rather small, unless you do low-level stuff (I remember Fortnite WoA port taking almost a year from announcement to release due to anticheat).