The Earth's rotation does not cause us to fall off the surface because we are bound to the planet by gravity. Gravity is the force that attracts objects towards each other, and it is responsible for keeping us firmly planted on the Earth's surface.
Gravity pulls all objects towards the center of the Earth. As the Earth rotates, it spins around its axis, causing a centrifugal force that acts radially outward from the rotation axis. The centrifugal force is a result of the inertia of the objects on the rotating Earth. However, gravity is much stronger than the centrifugal force, and it pulls us towards the center of the Earth, effectively counteracting the centrifugal force.
In simpler terms, the gravitational force between us and the Earth keeps us grounded. It pulls us inward, preventing us from being flung off the Earth due to its rotation. So, even though the Earth is spinning, we remain on its surface due to the gravitational attraction that keeps us bound to it.
It's worth noting that the perceived effects of Earth's rotation, such as the day and night cycle and the apparent movement of celestial bodies, are due to the Earth's rotation relative to our reference frame. In reality, we are in constant motion along with the Earth, thanks to gravity.