I look at app stores and see a lot of "free to play" products. So many users have gotten so accustomed to not paying upfront for products (which historically could be substantial amounts) that the option is often no longer available.
Affinity targets professional users who would purchase Adobe products otherwise. Professional users are more willing to pay for products. Affinity was doing pretty well in the Mac App Store (though they moved to free download + in-app purchase or purchase through their website).
