Why not quit if the match doesnt favor your tank?

iScending: As others have pointed out there are many reasons, however, the most important one is this:   If you leave the battle before it's finished you will end up getting punished for it.   This can be anything for a 24 hour to permanent ban, depending on how frequently you'd do it. Add to this that it's very unsporting and tremendously egotistical and I'm sure you'd agree you would be frustrated if someone kept doing this to you.