Being able to create polygons with infinite points would screw over existing maps, and it's just unfeasible; what if you draw a rectangle counterclockwise when Soldat is coded to solidify points which are organized in a clockwise fashion? It would just mess everything up. Triangles are the easiest and simplest.
BTW, there are more than 2 editors
MapMaker Plus by Mark.jp was the most prefered before PolyWorks, which I also now recommend.