By "misaligned incentives", I mean that we were rewarded with a % of ad spend. This is very common model in the old advertising industry, and AdWords was treated as adverts, not as a technology proposition. Of course this meant that we had very little financial incentive to reduce the ad spend.
A more aligned structure would have been to reward percentage of profits, but companies were reluctant to reveal their profit margins to a third party, and third parties couldn't trust their clients to report this data correctly anyway. Hence percentage of ad spend was what everyone used.