Incentives don't work if nobody knows about it. You wouldn't be safe if your nuclear bomb-vest was concealed. You'd just be a walking timebomb. As to which estate gets to deal with the class action suit, since any and all possible witnesses have been vaporized, the only one we can conclusively prove to have been at the scene is you, with your vest. And since you're not around, either, to point the finger at the robber, well, guess who gets the blame for the smoking crater in the middle of the city?
Well, in your world he'd have to assume I'm armed. Which would deter him. Right?
I'll just have to stream a camera feed to the cloud to prove my innocence should a class action arise. Problem solved.
But you specifically said that the criminals would be incentivized not to attack you, and the people around you incentivized to keep you safe. Those incentives would not work in the least if your nuke-vest is a secret. There's a distinct difference between "assuming you're armed", and "assuming your death will wipe out a significant section of the city"
And even assuming the EMP from your demise doesn't wipe the record of it, the robber killed you, but you killed all the others. especially if you didn't advertise the fact that your death would create a crater 3 city blocks in size.