1) Macs are harder to consider secure, they're effectively all jailbroken. Cheating/bypassing in app purchases will be rampant, reducing the opportunity for cross play, and the Mac market isn't big enough itself. These aren't insurmountable issues, but they require investment, and the additional Mac market probably isn't worth the outlay and risk.

2) You have to rebuild the UI, which costs money which the Mac version may well not recoup.

3) You have a different version for desktops that costs more upfront with less reliance on in-app mechanics that you don't want to undermine.

> "Macs are harder to consider secure, they're effectively all jailbroken."

OK, but that's no different to Windows and Android.

> "You have to rebuild the UI"

No. Even with apps this is no longer the case (see: "Mac Catalyst"), but it's certainly not true for games. Maybe you'd need to add some keyboard/mouse bindings, but that's about it. Even iPads support keyboards and mice now days!

So if an ios title uses a multi touch gesture how do you replicate that on MacOS?

Every MacBook has a multitouch trackpad. It's rare that I ever use a mouse.

Still doesn't account for desktop devices. And no, it's not a given that every desktop mac user has a Magic Trackpad.

You can do those multitouch gestures on TouchBar /s