Essentially all large aircraft1 have flight control surfaces powered, either directly or indirectly, by hydraulic actuators, as do most medium-sized and some small aircraft. Small- to medium-sized aircraft with hydraulically-actuated flight controls essentially always have some form of manual reversion capability, where the primary flight control surfaces (always the elevator and ailerons, and sometimes the rudder as well) are operated manually by the pilots, usually by control cables attached to the pilots’ yokes and pulling (depending on the aircraft) either on the control surfaces directly or on servo tabs which then generate aerodynamic forces which move the control surfaces. This allows the flight control surfaces to remain operational in the event of a total failure of the aircraft’s hydraulic systems, albeit requiring the pilots to exert a (sometimes considerably) greater force on the controls to operate them.
Large aircraft, on the other hand, generally have no manual-reversion capability at all. This is ostensibly due to the greater aerodynamic forces acting on their flight control surfaces at cruising speeds, which would require superhuman strength to completely overcome (despite the fact that, before hydraulic flight control boosting came into wide use, many, many large and fast aircraft were successfully flown with purely manual controls through the use of a number of force-reducing tricks). However, in a no-hydraulics situation, having any manual control capability at all, even with a significantly- to considerably-reduced control authority and range of movement compared with hydraulically-boosted operation, would be an extremely-useful adjunct to throttle pitch control and steering (which – especially throttle steering – are difficult, sluggish, clunky, and only really usable for coarse altitude and flightpath adjustments). So why don’t large aircraft have at least partial manual-reversion capability, despite even a little flight control authority being far, far better than nothing at all?
1 I'm using "large" here to mean "larger than a 737 MAX 10".