Users, absolutely. Some apps have already done this (Deliveries and Paprika Recipe Manager come to mind). But it's a ton of duplicated effort right now to do that. Paprika's Mac version costs $30 to compensate. There's much less competition here; iOS has a bunch of recipe managers but as far as I know this is the only one with a companion Mac version.
Maybe Facebook will make a Mac client for Messenger (messenger.com works, but some people might prefer a desktop version). Maybe Netflix will have a Mac client (they already have one in the Windows store). We could get Google Maps as an alternative to Apple's native Maps app. Slack could throw away their Electron battery-guzzler and replace the Mac version with one based on the native iOS codebase.
Not every app wants or needs a Mac port, but there are plenty of cases where it could be useful.
Maybe Facebook will make a Mac client for Messenger (messenger.com works, but some people might prefer a desktop version). Maybe Netflix will have a Mac client (they already have one in the Windows store). We could get Google Maps as an alternative to Apple's native Maps app. Slack could throw away their Electron battery-guzzler and replace the Mac version with one based on the native iOS codebase.
Not every app wants or needs a Mac port, but there are plenty of cases where it could be useful.