Naturally I know that.
But still to be more relevant & gain traction Swift has to add support for Windows & Android.
But what I am trying to say is that why stick to Swift when there are other alternatives available which are more matured and better.
Generally one reason is ignorance about existence of such a better alternative. Which I feel is very common in Mac only users. (Please note I am not trying to insult anyone here it just an observation based on users I have interacted with.)
Take for example the all powerful and fun to use Pinegrow Web Editor.
It is a fantastic web editor which was originally a Mac only tool, but could not garner much users so they had to release Windows and Linux editions.