Royalty gets grandfathered in basically. Of course all royalty got their land the old fashioned way: by rounding up a bunch of men from nearby villages and raiding their neighbors and killing enough of their subjects until they agreed to give it up. Or just outright killing the neighboring kings. War is not a new thing.
As long as Kings are content with what they have today we leave them be. It may be outdated and unfair, but its stable and usually not too terrible for the people. The alternatives may not be much better either, especially in countries with high levels of corruption. There is a hope that all monarchies will eventually crumble and be replaced by something more representative now that the concept of divine right seems quaint and out of touch, but power tends to be self supporting so it will likely take a long time.
As long as Kings are content with what they have today we leave them be. It may be outdated and unfair, but its stable and usually not too terrible for the people. The alternatives may not be much better either, especially in countries with high levels of corruption. There is a hope that all monarchies will eventually crumble and be replaced by something more representative now that the concept of divine right seems quaint and out of touch, but power tends to be self supporting so it will likely take a long time.