I know! And when a bird snatches them, they scream their heads off in hope to startle the bird into dropping it; I saw a Mississippi kite fly off with one once, this technique didn’t work 
I think I just answered your query; they are so loud and they know it, they know they are attracting predators as well as mates, and when you crunch by them, they are afraid you are one of their predators, so they go silent to prevent you from knowing their exact location, in hopes that you will move on :)
I’ve been a carpenter all my life. I’ve found that an electric circular saw and other power tools will attract Cicadas. Sometime landing on the tool while it is running. Sometimes more than one flying around bumping into your head. Very distracting. I’ve experienced this occasionally over several decades. I have a post on INat of a Hieroglyphic cicada that was attracted to my saw.