A keyboard and mouse should always be supported by any program that runs on a computer in order to interact with that computer program at the basic level. But who in the f*ck plays games like these with a mouse and keyboard? Some games are meant for mouse + keyboard, and some are meant for controllers. You wouldn't play a fighting game or a racing game with mouse and keyboard. Likewise I wouldn't play a first-person shooter or an RTS game with a controller. You use the right control method for the game type. Metal Gear games are controller games. Doesn't make sense to whine about the lack of mouse and keyboard support for games like these, or say you're not gonna buy the game as a result. If you're trying to play a Metal Gear game with mouse+keyboard, you're doing it wrong. I don't give a sh1t about the Metal Gear series so this doesn't affect me (though I did enjoy the 3rd game MGS1 on PS1, and I also really f*cking enjoyed MGRR), but complaints like these are just silly.
On the other hand I spent years complaining about the lack of keyboard and mouse support on consoles, and I'm glad Microsoft finally started changing things in that regard. Of course there were earlier examples of games on consoles supporting mouse and keyboard, like Quake 3 on Dreamcast, UT3 on PS3, Doom on PS1, etc.