Although it would be certainly nice to be able to deploy on Mac and Linux too, the PC/ Windows platform still has a player base second to none - Steam alone has 100 million registered accounts and at least 75 (%) of them are active users.
No matter what the engine/ product says it's not like you can port the game to various platforms with a single click, there's always more stuff to be done, for example have different Windows, Mac and Linux computers for testing. If you haven't managed creating a complete game for the PC alone yet (no offense!) I wouldn't suggest targeting a release on multiple platforms for now.
Pretty much hits the mark.
However it is always nice to have the OPTION to deploy to another platform, although this means further adaption.
Let's face the unreality you all of a sudden have a huge success, get requests for porting it here and there, and then are stuck with Windows only platform. While code can always be reprogramed if there is no other way, it... kinda sucks...
