if you're talking on the train, people know what you say, the other side is still pretty private.
with open radio, anyone on the train could be saving a hi-fi copy of the entire conversation.
in your analogy, he would have to be pushing a recorder between your ear and phone. very different from sitting in your door steps.
but i agree, the current system is crappy. I never bother to use bluetooth. but removing pairing instead of fixing is dumb.