There are different types of reasons to account for the reversal effect in different areas of human endeavour. Policies always cost resources to implement. Furthermore, the costs are not just linear. One additional dollar spent will not always give one additional increment of program output. Instead there is the onset of diminishing returns to scale and to scope.
Performance improvements start to cost more and more to achieve smaller and smaller gains.
So both absolute amounts of dollars, and their relative efficiency to purchase results, are limits on the policy thrust. The social world is growing increasingly complex, so the results of policy initiatives may be counter-intuitive. Other aspects of society that appear to have little or no relation to a problem, may nevertheless be effected by a policy or program. The intended target may even receive direct and important benefits, yet the subsidiary effects in other areas might leave a wider segment, or a more important situation far worse off. Consequences are the future effects of present actions.