>>46548485The reason that 6v6 battling isn't the main format for competitive:
1. It takes too long for a single battle to complete compared to doubles(usually less than 7 or 8 turns at the most)
2. It isn't spectator friendly
3. Gamefreak(probably but I'm damn near 100% sure) doesn't want a competitive format where stall tactics can become popular, due to both reasons #1 and #2
As for why it isn't supported in its own ranked ladder and battle facilities? I honestly don't know, I know there are a ton of 6v6 players and they deserve something too.