Well, about the trading, I don't know whats the point about that. I mean, if you hacked a great pokemon just to trade it for another one, then hack the one that you want and that's it! So, my theory is that the dudes who hack pokemons for trades just want to make people happy.
Think about it, you get an awesome or rare pokemon that you want for your awesome or rare pokemon that he/she doesn't care about.
Sure, maybe your Mew or something is from an event or shiny or who cares, but dude! you still get what you wanted in first place.
So, hacking is about giving, is about people getting great hacked and unofficial pokemons for stuff that the other guy don't really cares about.
In battles, is another thing.
If the poke seems legit, then I don't see the problem.
There is a thing, called Shoddy, that's about pokemon battles.
You don't have to train to fight in there, you just need to come up with a good team and strategy, and in a battle, predicting is a mayor part. And that folks, is skill.
Yeah, I won some battles and I losted a lot, and that's because my team sucks and im very bad predicting. But hey! im having fun, because I like to battle (and also, I like to lose) and guess what, I didn't even had to train my pokemans! How cool is that?
Yes, everyone likes to win at a game or something, and yes, hacking is not the way that the game is intended to be played, but if for some people, a game seems work, then is no fun at all.
I don't hack so I don't really know, but that's my opinion, and who cares anyways?