Why doesn’t Slack write an actual Mac app in Swift? For small companies with limited resources, I understand the attraction of “cross platform,” but it would seem that performance and uasability would be vastly improved by writing actual native applications — especially for a billion dollar company that can afford to do it and especially since Slack is one of those apps that is constantly open and performance and efficiency have a real benefit.
The only way this will change is if Apple starts using more "stick" approaches. Marzipan and whatever other technologies they're working on are the "carrot".