Couldn't let that one get by . But hey -- they have horns you can put on motorcycles now!!
This is true... however, a horn has an element involved that requires activation, which is a failure point from a safety standpoint, unless you glue the actuation device (button) down. In other words, the rider has to notice that a potential hazard has likely not noticed them and acted on that by hitting his horn button, whereas motor noise is a constant and is an indicator to someone like the blind folks in the story above to simply not step into the road.
I AM being silly about this, btw.