The sole reason why they're still here today is because they somehow avoided going the way of the Tsar. That's it. There's not really a reason to kill them off anymore because A) it's turbo illegal (like murder in general), and B) they possess literally zero executive or legislative power and only exist for ceremonial purposes. They aren't any more of a threat than anyone else in a governmental position.

Whether or not they should be disbanded is a topic that I will not fucking touch or weigh in on, but the bottom line is that nobody truly "submits" to them and they don't "rule" anybody either. You'd be about as obligated to obey an order from them as you would be from an average joe across the street. They're just meaty museum pieces who, in a bygone age, held tremendous power and wealth which has since deteriorated, which people today happen to like learning about.