Just to return to your original question, what caused you to suspect
that gliders needed power assisted controls ?
AFAIK, there is no power assistance in the common Cessna and Piper GA
aircraft, unless you are using the autopilot. Am I wrong in this
assumption ?

No, you are not. rudder, ailerons, and elevators are direct cabled with
no power assist. Cessna (from the early '60s on) uses an electric motor
for the flaps but even this was un-necessary, IMHO, for the 182 and below.

Tony V.