Indeed. I suppose that another way to look at it would be that in order for someone or a computer program to try to produce a perfect circle using quadratic Bézier curves, that an infinite number of quadratic Bézier curves would be needed: so at some stage a decision needs to be made that the number of quadratic Bézier curves being used is enough for the desired effect.
On a different aspect of this matter of quadratic Bézier curves, I am including here a link to how I used quadratic Bézier curves in producing my Sonnet Calligraphic font. There are two illustrations that will hopefully be of interest.
This is because I thought of a technique of producing a design for a calligraphic curve by starting with straight lines, then converting all of the on-curve nodes to off-curve nodes and then adding an on-curve node half-way between each sequential pair of two of those off-curve nodes. Adding the on-curve node half-way between each sequential pair of two of those off-curve nodes does not alter the shape of the curve, yet does mean that each quadratic Bézier curve is defined from an on-curve point to an on-curve point, with possibly an off-curve point between them.
What I really like about those two diagrams is that the design is based mostly on several long thin rectangles, with the change of width from rectangle to rectangle quite dramatic; yet the final result has the continuous calligraphic curve varying in width smoothly from thick to thin then to intermediate width and then back to thin, all as a result of the quadratic Bézier equations.
William Overington
8 June 2012