Simple.. cowards shame adds a mini loss? I think you people are thinking about this too deeply. The idea is that some people are useless, and will lose more minigames because they don't help their team. So balance the useless people out via minigame loss stats.
I personally have a 2:1 minigame win/loss ratio on one (rather new) character, 3:1 on another. When I start a fresh 80 and join minis, it's easily 1:1 or 1:2 until my gear is better, because I was not able to help my team as much; so they were effectively down 1/2 a player because of me.
All that gear calculation, and (in Deathwish's case), you get fully geared people like Dashtemargo, Ashtyphoon, and Sombreza, who are selfish and do not play for the team.. They focus the wrong targets and don't play as well as an average player would.
Ashtyphoon: Stands there and casts 1 spell every 3 seconds, worse than pikuu
Dashtemargo: focuses heavy while clothy burns him down, heavy lives.
Sombreza: Doesn't even pvp, just goes for the flag and dies over and over.
The thing is, balancing on KDR or win/loss, with people "pad" their stats, will assume they are a great player and will pair them with weak players, which in effect will ruin their stats and balance out over time.