why does the cutscenes on here use weak keyblades like in this video where they use the kingdom key http://www.kh-vids.net/newplayer.php?id=tDY0EtUIOAQ
Why not? What Keyblade to use in battle is a preference left up to players; perhaps the Kingdom Key was just the one chosen to be used in the video. As for why *all* (apparently) the videos use the Kingdom Key, the same reason applies. Taking into account that these were meant to be gameplay vids for the public, perhaps using the Kingdom Key would've felt more canon than any of the others.
Because only cool people play the game with the default keyblade. Most gaming companies only release videos/pictures with the default weapon and maybe 1 or 2 others so that it doesn't ruin the surprise of getting a new one. I guess DS was doing the same thing. Or he's just pimp and uses Kingdom Key.
Exactly, your not cool if you can't use the beggining weapon you start of with all the way through the game and it's probably because most of those keyblades ain't canon and Kingdom Key is Sora's Canon Weapon as you see in the Intro to Kingdom Hearts 2.