BrandeX: Perhaps, but Mortal Kombat (1-3 collection) IS on Steam, Amazon, and many other retailers.
It's also loaded with Microsoft GFWL DRM which requires you to create 2 Microsoft accounts to even be able to play the game single player and only then with an active Internet connection. The likelihood of them using such toxic draconian DRM on games that are 20 years old and then magically waking up tomorrow and saying "yeah, screw it, let's re-release MK on GOG DRM-free!" just seems incredibly unlikely to me. What's more likely to happen is that when GFWL gets shut down in July as planned, all of the games that use GFWL DRM will cease to function permanently unless the owner downloads a crack for the game and uses it. A little reward for buying the game - having to crack it like a pirate to be able to play it even in single player only mode.
It'll remain to be seen if the MK games get updated to remove GFWL DRM before GFWL dies, but if they do - they're likely to just replace it with some other equally obnoxious DRM or at best just use Steam's less restrictive DRM.
Having said that, I do hope to be proven wrong come July 2014. :)