I'm sure it comes of being EXP, although I've seen a few other cases where EXP did not get it.
It must be the same disarming demeanor that has mrs. brp annoyed that I never get traffic tickets (been about 6 or 7 times when she's been with me over the past few years). Like the other night when I got a "you should slow down" after being pulled off the freeway for (supposedly) doing 80 in a 55 zone. (In my partial defense, the freeways in CA are just about all 65, and I have no idea why this was 55...and hadn't noticed, and I really don't think I was going over 75
)
I've certainly had to pay when I was EXP so that's not the complete answer.
In some cases I've been lucky with traffic tickets because I still speak the Queens English, the best of those being in SD where I got stopped by the Sheriff of a small community who couldn't figure out how to get the details from my pink paper English license into his book of tickets. I suspect he let me go rather than demonstrate his literacy, or lack of it.