An elliptical planform does not generate zero induced drag. Induced drag is merely a minimum with elliptical lift distribution, but only slightly less (<10%) than that of a moderately tapered wing. In fact the elliptical form is only more efficient when a constant wing span is considered. For a constant area and root chord, a tapered wing with a little wider span will be more efficient than the elliptical form with a shorter span. With an elliptical planform each section operates at the same angle of attack across the span which is most efficient in producing lift. However it also means that the entire wing will stall at the same time which gives a rather abrupt stall.

There is no free lunch. Induced drag is the cost of producing lift in the real world and in spite of his grace and beauty, the hawk has to deal with it also. Tip design and planform do influence induced drag a little, but the cause of induced drag is the fact that the wingspan is not infinite. Higher aspect ratio (wider span) and lower wing loading are the only two factors that have a great effect on induced drag. Aspect ratio is usually limited by structural concerns and as wing loading (and induced drag) goes down, form drag goes up.

As a practical matter, induced drag only becomes significant at higher angles of attack. In normal flight profiles this is when landing where the higher drag allows a steeper approach without picking up excessive speed, which is a plus. One exception to this is pylon racing where minimum drag during steep turns is a major factor in overall speed.

Wing design depends very much on the desired mission and is a compromise between several competing factors. There is no one magic configuration.