A variety of reasons, but the main ones are...
1. They have too many variables. A person could post their team, and somebody else could change all of your team members. And at the end of the day, all that is really doing is making another separate team that isn't really much better than the original. There are too many viable moves, too many opinions and basically too much everything for things to work. There was a time when we allowed them, but they caused too many arguments and the suggestions were too brief so we banned them altogether. People were also saying things like "I can't get that Pokemon" or "I don't like that" which caused problems.
2. They aren't competitive enough. What I mean is, if you are a good player, you could beat the game with nearly anything, and if you lose you can just go and try again. It is just too simple and easy. This is why only teams that are used online are allowed since if you lose there is no turning back. The amount of moves you can use with success and the number of viable Pokemon are both lower in competitive/online play, so improving teams is more simple. Competitive also follows rules like tiers, clauses etc. and since there are so many different metagame, almost every team will be different compared to in game where many Pokemon use the same Pokemon making things bland and very boring.
Hope that wasn't too hard to understand, I ramble a lot I know ;P
Dec 22, 2013
by
Fizz