Very often an arc is drawn to connect two already existing points, so that the lines, these points belong to are tangential to the arc. Now it is necessary to build a center point first. This is no easy task if the angle between the lines is not straight. One has to build two perpendicular lines from the points and find their intersection. So much work for nothing, because the angle between two lines and two points is all what it takes to build the arc.
A new tool "Arc from 2 points" would satisfy this use case. The user selects two points and presses Enter. In the tool dialog the angle of the arc is entered. To generate center point or not can be left as a tool option.