Scout implies someone who primarily gathers information by quickly moving ahead of a larger traveling and coming back. Because he is swift and has a nonviolent purpose in a military context, games tend to depict scouts as weak, or only useful for information. The universe has few coincidences and more correlations.
Scout is only meant to improve your draws, so it signified a card restricted to informational advantage. It doesn't make any $ or cards and definitely doesn't attack, so it ended up a bad card. The TF2 scout has light firepower, and high speed, which makes average health a very dangerous balance move in a game like Capture the Flag. Starcraft scouts are actually scouts, the idea is to look at your enemies army with them. So they are weak.
Teemo, the Swift Scout is a very weak champion in League of Legends, (could be fixed by now, but he's been weak for the majority of the lifetime of the game). He has less firepower than other units and less health to go with his scouting theme. He moves quickly, but it doesn't matter much if he can't fight well.
Just when Asperger's on this thread