Simple. The game doesn't do a good job at explaining any of this (hell, the tutorial doesn't really do a good job at explaining the basic game).
When you are a new player and constantly see people going off for half a dozen kills early and snowballing, while you are just trying to stay under 10 deaths, how do you think it looks? Only when you see actual comebacks do you understand it's possible, but since you probably aren't contributing to said come-back (because you don't know how, you don't know it's possible, etc), then you probably WONT come back, so you never seen them to believe them.