…Because the games runtime engine is browser based (html5) and the Construct editor isn't.
I use Parallels to run Construct on the mac, but you will have to wait for Construct 3 for native editor support.
Construct 3 is gonna be for mac? Also I thought it doesn't work in Parrellels, I've tried it in WineBottler but it won't pan and you can't debug or test the game :p