That's not true. Incentives aren't the whole cause of behavior and they aren't the solution to changing it either. That's the same simplistic and flawed mentality that pushes for harsher punishments to deter crime when the evidence shows that doesn't work and that not even death penalty is an effective deterrent. People have several incentives to lose weight, but increasingly they still overeat.

Incentives play a role, you don't want to encourage wrong behaviors certainly, but they're just one factor in determining what people do or don't do. At best, they nudge. Those nudges aren't likely to overcome stronger forces, or even several weaker ones.