Limits on how much parents can spend other people's resources on their kids. Which goes with civil office being a job rather than a special privilege.
It's dishonest of you to argue that they should be treated like normal citizens while they cling desperately to their distinct and superior position. If they want to be treated as normal people all they have to do is renounce their titles.
King Albert 2 didn't want to become king but nobody else with enough capability was available. So it's not just a fun job.
But yes, the discussion to king or not pops up once in a while, and the general response seems to be we got much bigger problems.
Oh wait that’s Brave New World. Or The Naked Sun, depending on your preferred flavour of SF nightmare.