I rarely leave matches. Some of my most memorable wins were coming back from what looked like an impossible situation, rallying team mates, or giving advice to those who didn't fully understand a warzone or pvp mechanics. I've even had some losses that were a lot of fun. I bet that is an impossible concept for some people to grasp.
Most of my matches are huttball and I often see guildies and friends on the other team. I'd rather have a challenging fight against them than quit real fast in hopes to complete a quest.
The few times I did leave were when lots of people went afk or openly exploited. I've been PvPing since early release day one and have left less than 10 matches, if that. In those rare circumstances, I would still leave with a penalty, if I saw those things going on. There are legitimate times to quit a match, but they are few and far between and it certainly has nothing to do with completing a daily quest, fear of losing, or not feeling like a special snowflake in shiny gear.
Even though Bioware/EA has made mistakes, the player-base is just as bad when it comes to bringing negativity into the game.