Well, obviously, VGC stands for Video Game Championships -.- The tournaments weren't set to VGC Rules - VGC rules were made for the tournaments. The meta isn't particularly weird, if you do realize the Pokemon is a Japanese game. The Japanese moved from Singles 3v3 to Doubles 4v4 when Ruby/Sapphire came out. We Americans stuck to Singles 6v6 since RBY, and continued all the way through Generation V. This isn't an "American" metagame, but rather a Japanese one, so that's why the rules are so weird to you. Also, the Unova Dex only rule is to make the metagame fresh - after three years of seeing Metagross and Snorlax everywhere, and after discovering all the usable strategies of previous generations, making it Unova-only forces everyone to rethink their strategies and ideas, and practically start anew.