They focus on individualism; create competition and conflict between kids where complaints of unequal treatment and playing favorites are common. It interferes with efforts to promote collaboration, cooperative learning and a sense of community which improves the quality of learning.
Rewards also interfere with a genuine and trusting relationship with a teacher where a kid feels safe to be open, expose his vulnerability, admit mistakes and ask for help when problems develop. It is the judgmental nature of rewards and praise that encourages kids to try and impress and curry favor with the person handing out the rewards. Rewards are a tool for ' doing to ' kids, control and manipulation through seduction, rather than ' working with ' kids in an unconditional way. Kids feel valued and accepted only if they behave as they are told and do well in school.