Legally and historically talking, they are irrelevant. They could disappear that the democratic REgime would still work damn fine in most case. In Belgium it is a bit different but it is all another case, maybe here Albert is kinda gathering the country in one piece but once the situation will be fixed over here, the King doesn't have much significance neither. As for England.. well, they are used as promotion tool from time to time but that is all. I wouldn't advocating to give them the guillotine but I would certainly be in favor that the State stops to give them any high royalties though.