I would speculate yes. (1) You want subjects in the control group to be incentivized to maintain contact with the researchers throughout the study and be willi

I would speculate yes. (1) You want subjects in the control group to be incentivized to maintain contact with the researchers throughout the study and be willing to spend time answering their questions. (2) Whenever feasible, you want all subjects in a research study to be better off than not participating in the study. (3) It also controls for some minor confounding effects like "gets in the habit of going to the bank monthly and cashing a check".