As you create curves, the size of the Create Curve brush 
determines the amount of space between curve points, effectively establishing the resolution of the curve. Using a small brush Size value produces more curve points and a higher resolution curve.
(B + drag to adjust the brush size, or set the Size value in the Curve Tool properties.)
The curve resolution influences how much you can control the shape of the curve, which becomes important especially as you modify curves in a manual remeshing workflow.