Is that why quaternions are interesting for computer graphics? I studied mathematics and computer science but never understood (or even looked so hard into) the connection.
The killer feature is that you can put the two together for a rotation axis (~ vector) and angle (~ scalar).
With just three gimbals (rotating circles), if gimbals A and B are aligned, you only have two degrees of freedom (rotating A is the same as rotating B). Because of this, interpolating angles is unwieldy in vector space. 'Gimbal lock' confounds animation (in hilarious but unrealistic ways) but also aerospace (four hours before 'one small step for man', just after landing, Collins joked he would like a fourth gimbal for Christmas).