Earlier quoted context omitted.
Cars come equipped with horns for that exact purpose (alerting pedestrians, etc.), though they are often used as displeasure-signalling devices.
As a cyclist it's often helpful to be able to hear the sound made by cars moving across a street, for example, when approaching an intersection where perpendicular traffic should stop, but may not.
I would love car traffic to be more silent but AFAIK the tires actually make most of the noise.