Three.js: why circleGeometry has not an height parameter so it could be turn into a Cone easily

if circleGeometry has an height parameter it would be a coneGeometry automaticly. As far as i understand you already doing it with cylynderGeometry wihle making its top circle's radius 0. but if we build things up from the bottom it would be most beautiful way indeed.

-> give circle a height parameter (if height is 0 its a circle)
-> if height is not 0 its a cone
-> create cylinder two circle and planes between them

Is there a specific reason why you did not it this way?