Luck plays a part in any game or match-up. W/L/D is just more loose in the matches, since BP games will match a 20VP player and another 20 VP player, where WLD will match two W's, one of which may have only beat their opponent by 1 VP, while the other got a decisive victory. WLD also makes it more likely that the lists everyone hates will get matched up against the attendance base as a whole, rather than against lists that performed proportionally as well.
/I personally hate W/L/D.