Because it feels good to receive them. You feel appreciated, and it strengthens your desire to keep playing when things are a bit down.
That's why I give them. To make people I like having around feel good.
Sure, it's not as if receiving a medal is the highlight of the year, but still. It feels good when you put a lot of time in a team game, and others recognize your contribution. We'd gain nothing by abolishing them.
Woah. I agree with Chénier. Is the end nigh?
