Power centralization and distribution/decentralization both have their respective benefits and disadvantages. By retaining some power in the counselling room, the counselor ensures that he/she can control the session; the roles are well-defined and supervised/controlled by the counselor. It also helps in reaching quicker decisions and conclusions and thus speedier sessions and processes. Clarity about authority and accountability means any difference of opinion can be resolved quickly and will not be dragged out (unlike decentralized power distribution, where all the power centers will try to control the proceedings).
The disadvantage of power centralization is that the counselee (the person getting counseling) may not be very comfortable with one-way control and may feel inhibitions in sharing all the information. Another issue is that the decision reached or conclusion arrived at may only appear comfortable to the counselor, however the counselee (despite disagreement) may accept it due to a lack of any other option.