Hi Robbie,
As Dwayne has mentioned, there are many reasons for disabling the ‘deform’ option on bones.
In this course (the next chapter in fact) you will learn the 3 main purposes for all bones in a rig.
Deform bones, Mechanism bones, and Control bones.
Control bones are the ones you animate, the mechanism bones are there so the rig functions in the way you need (an IK chain for an arm, for example), and Deform bones are the ones that moved the geometry, but they are pushed and pulled by the other 2 types.
I won’t give you any more spoilers 😉 but I hope you enjoy the course.
Fun fact though – there are often way more bones in your rig that DO NOT deform the geo that do.
