the big deal is that the whole point of traffic protocol is to ensure that driving behavior is standard, expected, and PREDICTABLE. if i have the right of way, i take it. if i don't, i don't.

how many times have you, on a bike and stopped at a 4-way stop, waiting for a vehicle to your right (perpendicular) to proceed after arriving at the intersection first, said driver waves at you to go ahead ? while this courtesy is appreciated, i never take him up on it (unless perhaps it's rather obvious he is doing more then being nice, like looking at a map or otherwise "stopping/pausing". i will not go because if he decides to go and hits me, guess who is at fault (and also severely injured) ? that's right, ME. your suggestion above violates the entire expectation of PREDICTABLE behavior.