But no scientific study has ever found a long-term enhancement of the quality of work as a result of any reward system. Bribes and threats can get you a short-term effect, but that's it. Kohn says rewards may actually damage quality and productivity, and cause employees to lose interest in their jobs. Rewards control behavior through seduction. They're a way for people in power to manipulate those with less power.
Rewards ruin relationships.
They emphasize the difference in power between the person handing out the reward and the person receiving it. Rewards create competitiveness among employees, undermining collaboration and teamwork. Rewards reduce risk taking, creativity and innovation. Rewards ignore reasons. The bottom line on growing the top line.