>go on for glory
>win 15 games in a row
>other person wins once
>taunts
>leaves
why does this occur so often?
If you want a non-meme answer, it's because the people you're fighting are only half-serious about the game. That's why they stick with FG instead of Smash Ladder.
They take the game seriously enough to enjoy winning, but not seriously enough to enjoy getting good. Basically, you're fighting /v/. "Too good for my friends, too bad for anyone else" is a good description.