Why does Earth keeps rotating in its own axis?

Answer 1

Inertia. A child's top, or gyroscope, or dreidel work on the same principle, but the toys are subject to friction and will eventually stop. The earth has friction losses due to tides, but the energy loss from this is relatively small -- but it does cause the earth's rotation to slow by a measurable amount.

Answer 2

All the planets rotate because of the gravity of the sun and the planets orbital motion.
The rotation of the earth is actually decreasing indicating
most of the rotation came when the earth was forming into
a planet.
However some of the rotation comes from the fact we are
orbiting the sun in an ellipse and the suns gravity adds to the rotational effect

Answer 3

Earth, all other planets and even Sun rotate about their own axis, since all of them formed from a cloud of gas which condensed and in that process, spinning started. They also rotate about a common centre, in our case the sun, which rotates about another star system etc. Rotation and spinning seems to be inherent properties of many if not all stellar systems.

Answer 4

To keep us all on the planet.