Louder sounds (within our range of hearing) will be easier to hear. INCREASING OTHER PEOPLES AWARENESS. How does that not make sense to you? That doesn't mean people pay enough attention, or can tell where the noise is coming from. Given how quiet most modern cars are inside, and how little noise goes forward (where most threats are), it takes an outrageous amount of noise to get people to notice. If it's so much safer, someone has probably demonstrated it (rather than just saying they obviously do - lots of people claim something is obvious, that doesn't mean it's always right).