The reason for picking it this way is that rotating the [positive] x-axis onto the [positive] y-axis is about the simplest rotation you can think of, so we decide to call it “positive”. And clearly rotating the positive x-axis onto the positive y-axis is, in the normal way we draw Cartesian coordinates, anticlockwise.

Why are coordinate quadrants numbered counterclockwise?

The decision that a circle should be labelled counterclockwise was made by the ancient Babylonians long before any surviving mathematical works, so nobody really knows why it was made.

Are quadrants counterclockwise?

If we defined going to the left to be increasing then the quadrants would have been defined in a clockwise manner.