The reason was because at first it was just a small difference but Horde noticed it was enough that they could just make roving death squadrons. So, this incentivized Alliance to turn it off because if you're spending 5x as long to complete a quest for such a minute amount. The whole purpose was to have skewed rewards so the team that is outnumbered who is naturally going to die more is going to get enough to offset the difference. But apparently that couldn't be waited for and Blizzard just dropped the bonus themselves while once again we were still outnumbered and the gap was still at HALF what it was (so if it was 10 to 1 it is 5 to 1. If it was more, etc).