Why do computer mouses click?

A click is a reassuring way of knowing that something happened. A mouse that doesn't click is a distressing thing to use. It is caused by the mechanical switch operating, usually a microswitch.

The solution for you is to get a graphics pen. These don't click.

No, the clicking is just incidental, the point is that the sharp feeling you get tells your finger and therefore your brain that the click has occurred. How many times have you clicked on something and had to wait? Isn't it good to know that at least the mouse clicked. The nose also tells us whether there was an accidental double click etc.

There's a click sound because there is a spring beneath that button. The spring is there so that it bounces back to original state after you click on them.

You can try removing the spring to prevent yourself from hearing the click sounds. But note that your mouse will be less responsive if you do that.

The choice is yours.

Because there is a small button under the button that links the motion and the action together

It is an unexpected sound made my the mouse after it was inventedand we can't stop it......

it would be cool if they squished. or made a sigh...