Why not every degree of freedom needs its own motor — and why giving up one-motor-per-joint control is often the smarter design, not a shortcut.
Degrees of freedom (DOF) describe how many independent ways a mechanism's configuration can change — a purely kinematic count of joint parameters. Actuated jointsare a separate, much more practical number: how many of those joints actually have a motor, tendon, or other actuator driving them directly. It's easy to assume the two numbers should always match. They don't have to, and in a lot of good designs, they deliberately don't.