Why are the orbits of the planets elliptical?

The only way to have a circular, stable orbit is to have a static solar system. Not going to happen. Earth, for example, is pulled and pushed by the sun, all the planets and asteroids and moons and the galaxy itself. And let us not forget Dark Energy, which is expanding the Universe at an ever increasing rate. .
Imagine you are swinging a ball around your head, held by an elastic tether. Now walk on a treadmill while spinning around in a strong, changeable wind during a constant earthquake. Besides nausea, no way can you have a static orbit.