Simply put. It's such a load of shit, you get no benefits for being the king other than an overshield like once every 2 minutes.
NEVER get a lead as the king. EVER. You will lose. Not only will you have everyone on your dick, but you gain nothing at all from it. You will be worth 40 points a kill while you gain nothing. Literally nothing, there is no reason to try to maintain being the kill. It's best to die before you give others such a huge bounty and hope to get other regicides. Such is why this game-type fails spectacularly, trying to become the king is counter-intuitive to winning, as your point gain drastically lowers.
The overshield they give you every 2 minutes is laughable, straight up laughable. I played nearly an entire game being the king THE WHOLE GAME and what do I receive? A guy camping on the middle building in Outpost killing me and 2 others who were bum rushing me and him receiving a metron fuck ton of points, then it happens again because no one bothers to kill him because they just rush me some more. See? That is the optimal spot to be. So in the end I had 6 more kills and 8 more assists while dealing with the constant spam of shit my game, yet I still lose. It's a shitty mode.
So much rage, it's simply painful you don't get medals and points for staying king, IE Ballhog for oddball.
Edit: On a side note why does Promethean Vision have no counter