In the US, you have the current president as well as previous presidents attending international events. Hillary and Bill Clinton are obviously very famous, but even someone like John Kerry is highly regarded. I think removing the monarchy would shift the importance to key members of parliament (the UK equivalent of the Cabinet of the United States).
I don't see earned wealth as parasitic, so I have to disagree with you.
Yeah, I have no idea what ex-PMs do once they're out of office, but since taxpayers are still paying for their 24hr protection for the rest of their lives, they may as well put them to good use too.
Well, I wouldn't say all earned wealth was parasitic.
Someone like Paris Hilton, for example, who has improved upon it, works and has built an empire for herself, I wouldn't categorise with someone like Tamara Ecclestone who does... the opposite.