On macOS, applications can be sold outside of Apple's Mac App Store.
Many developers choose to sell their software through Apple's store in order to access the audience Apple provide.
However, there are numerous business reasons a developer might choose to avoid the Apple operated stores. These include control over pricing, product, and ...
There are a number of reasons developers may not want to go through the Mac App Store:
Apple Developer account is required with paid annual subscription of
Apple review process may block certain features or APIs
Apple determines that the app does not follow other guidelines (ui, content, etc)
Apple requires some features to be implemented or will not ...
Some developers don't like the App Store, and there's a wealth of reason why - Apple take too much money, Apple don't police the Store and stop the perpetual flood of cheap copies of decent apps, they don't like the restrictions placed on App Store stuff ...