The orbit of mars is never far from the ecliptic. why?

The plane of the ecliptic is an imaginary plane that passes from the Sun through the Earth. So Earth has an inclination of zero degrees from the plane.

All planets of our Solar System do not lie in this imaginary plane.

Mars is less than 2 degrees off which is why it appears to be centralized. Jupiter is also less than 2 degrees off. But some such as the Plutoid or Dwarf Planet Pluto can be off as much as 17 degrees.

Hope this gives you a bit understanding!