Its actually high risk / low reward for you, and low risk / high reward for them --
If you win --> you win very little // if they win --> they win a lot,
if you lose --> you lose a lot // if they lose --> they lose very little.
It keeps the ratings from getting slogged down. Everyone make mistakes and blunders, especially when moving fast, and you never know if that 300 player is just a prodigy that is at the beginning of their climb to the top. Always play to win.