# Questions about higher order Bézier Curves

I can generate the same Bézier Curve using my own code as the curve generated by Mathematica's function BezierCurve, but when I increased the order of the curve, it seems the graph I generated seems different from the one Mathematica generated.

I did it according to the definition of the Bézier curve, I do not know why. Can somebody explain it to me?

pointsGeneration[k_] := RandomReal[10, {k, 2}]；
parametricterms[n_, x_,l_List]:=(Binomial[n-1,Prepend[Range[n-1],0]] Table[x^i (1-x)^(n-1-i),{i,0,n-1}]).l;
a = pointsGeneration;
cc = parametricterms[5, x, a];
ParametricPlot[{cc[], cc[]}, {x, 0, 1}, AxesOrigin -> {0, 0}];
Graphics[BezierCurve[a], Axes -> True, AxesOrigin -> {0, 0}]


Options[BezierCurve] contains SplineDegree -> Automatic which seems to split a list of control points {c1,c2,c3,c4,c5,c6,c7,c8,c9} into {c1,c2,c3,c4}, {c4,c5,c6,c7} and {c7,c8,c9} so you get continuously joined cubic beziers except for the last part whose degree depends on the number of supplied control points.
Graphics[BezierCurve[a], SplineDegree -> Length[a] - 1, Axes -> True, AxesOrigin -> {0, 0}]