Well, one because your scenario shows a lack of knowledge of what competitive battling actually involves. Just because a Pokemon is an "event legendary" doesn't mean jack in terms of how useful it is in battles.
Celebi and Jirachi, arguably the two rarest Pokemon in terms of how many events actually were hosted to give them away, are typically in the "Overused" tier. They're good, but not so good as to be overpowered and banned to the Uber tier.
Phione is an event exclusive mon and is very underpowered.
And yes, if someone puts in the effort to get a Pokemon and train it, assuming that it follows all the rules the individual trainers' decide to enforce in the battle, they should be able to use it. Someone shouldn't be penalized because of what they have.
Should people who own Gen 3 games be told they can't use Gen 3 move tutor moves on their Pokemon, so that it's "fair" for players who only own Gen 5?
NO!
Those Gen 5 players can go back and get the older games if they wish. If they don't, tough. They'll have to make do with what they have.
(Also most competitive battling takes place over simulators anyway)
Does giving advantages to some competitors over the others makes sense?
People shouldn't be penalized for being successful at trading, collecting, and battling.
Well randomspot, I didn't really get the answer I wanted, you more or less told me why the event pokemon happen and what they are.
I wanted to know why your personally against it.
I'm not "against" anything. I'm just pointing out that people (not you specifically, people in general) are STILL complaining despite EVERYTHING Nintendo and the powers-that-be have done.
WAH! They don't hold events outside of the US/Europe
And voila, they do that.
WAH! They don't hold them at Gamestop!
They do that too
WAH! It's never on Wi-Fi!
They've hosted several events on Wi-Fi and Dream World/GL
Short of quite literally handing them to you (and thus eliminating the point of event Pokemon), I don't see what else they could possibly do.
Allowing Events to enter in a tournament is like giving running shoes to an athlete (just because he subscribed between 1 to 31 December) while others will have to run with horseshoes.
This is assuming that the athlete would never ever be able to get running shoes ever.
Just like ANYONE with money can purchase running shoes, YOU can go and trade for those events you missed.
"But blah blah blah blah blah"
That's an excuse.
What is preventing you from trading? If you say you don't have Wi-Fi, then I don't think you'll ever be in a situation where you'll be competing in a serious battle or at an official tournament anyway.