The only question you have to ask yourself, is why they changed Sub-Zero's freeze combination.
But for some unknown reason, they decided to port this game to the Game Boy and somehow realized how to suck out all the fun and release it onto store shelves.
The main problem with the game is the speed. Everything runs unbelievably slow like it's been sprayed with molasses and it's been fry for three years. It must be literally, 4 frames a second. I have no idea why anyone would do this to a game unless they got inspired by some memories of the old Speed Racer cartoons and thought that was a good idea to emulate.
Because the game runs sooooo slow, the timing mechanisms are all off compared to all the other versions. Master of the Super Nintendo version? Well that won't translate well over to this one as pressing the buttons too fast, or normal speed to do moves, will cause you to simply move forward or back and punch like a ninny. All the timing is off but even when or if you get used to it, it won't matter because it's just not fun to play. There's only six characters and the fatalities are very difficult to perform because of the aforementioned issue with timing.
If you can somehow play this game all the way to Goro, you'll find out that's he pretty difficult and when you battle him, you'll discover how laggy the game can really get.
Even the sound seems like it all came out of 1990s cellphone through a cheese grater. The music seems to have gaps in it and it really drags down the experience even more, if that's possible.
Finally, why did they change Sub-Zero's ice ball? Why does it have to use a kick to perform it? Why is is backwards? Why couldn't they have kept the move the same like they did in every other Mortal Kombat game? This game is completely nonsensical and I implore you to stay away as far as you can. Playing it for 2 minutes is funny. Playing it for 2.1 minutes is scary.