It is a deception. There is no actual improvement with drugs and alcohol. The mind is unable to compensate for the foreign chemical it's being subjected to and develops false responses as a result. The "euphoria" that is felt is one of the ease on the symptoms of withdrawal.
It most cases, the alcohol or drug acts as a placebo does. People believe they are better when on the substance. But again, that's the deception working. But that's the trap. Once the effect of the substance wears off, you want more of it. That's when the addiction and damage begins. You build up a tolerance and require greater amounts at greater intervals.
But it makes no difference to me. I've seen plenty of team games, not just in League, ruined by the mistakes of players who then claim that they are drunk or high as some sort of justification for their failure. Across the board, I don't like playing with people who are inebriated nor do I care to listen to their excuses that they have willingly imbued a substance that will ultimately make them less effective then they might have been otherwise.