Why are some apps only available for iOS?

There are really cool apps in this world available only for iOS. While Setapp has been a macOS-oriented product for many years, now we extend our focus: we additionally start providing apps that you can use on your iPhone/iPad only and not on Mac. And we call such apps "iOS apps." 

You can use all iOS apps if your plan includes a subscription for iOS devices ("iOS," "Mac + iOS," and "Power User" plans). 

Note: You cannot share and read "What's new" from them.

See also Install and activate iOS apps.