GSC OU is a physical metagame because all the biggest threats are physical. Snorlax is the best all-around pokémon in the game. Marowak, and Machamp to a lesser extent, are the only pokémon that can potentially pose a threat to everything. Dig a little deeper and Tyranitar getting an AP boost usually ends the game. In contrast, Snorlax basically beats all special attackers and most of them are also walled hard by Blissey. The few that aren't walled by the egg get stopped by Raikou/Jolteon instead.
Starmie can use Psychic as an acceptable neutral attack. It doesn't hit fellow Waters for double but it hits them for neutral (except other Starmie) while warding off Gengar and Machamp. Alakazam always uses Psychic and it's probably the biggest special threat in OU. (Encore forces Blissey out and stuffs Umbreon, making Snorlax and T-Tar the only good "answers" to it.)
And with regard to our poor, oft-forgotten ubers, Lugia is a way better pseudohazer than Skarmory could ever hope to be. :P Did you know: Lugia can survive a Belly Drum Double-Edge from Snorlax? Yeah, dude's a fucking tank.