[jacobolus]

My understanding is that most available CAM tools deal exclusively with circle arcs and straight segments.

Personally I don't think cubic Béziers per se seem like an especially good CAM primitive, but they are ubiquitous in 2d computer graphics, so they might be convenient for that reason.

[chrismorgan]

I have received the impression (as an outsider) that NURBS get used quite a bit in CAD and CAM too: https://en.wikipedia.org/wiki/Non-uniform_rational_B-spline