Why all the planets are inclined on their axis?

Damn good question. The short answer to this question is: 1. Conservation of Angular Momentum 2. read more

We don’t really know how the solar system was formed , but by observing the solar system in its present state, and noting down stuff like : rotation of the planets, axes tilt, distribution of components such as the inner rocky planets and outer gaseous planets; and observing other nebula and solar system processes we can only theorize, why they are tilted. read more

All the planets have orbits that are all roughly in the same plane called the ecliptic, but do not have the same obliquity. This rotation axis is never perpendicular to the orbital plane of the planet, but inclined at an angle varies according to the planets (see picture against). read more

Planets form from material in this disk, through accretion of smaller particles. In our solar system, the giant gas planets (Jupiter, Saturn, Uranus, and Neptune) spin more rapidly on their axes than the inner planets do and possess most of the system's angular momentum. read more