Why?1. She has considerable personal wealth which is used in the service of the State. For instance, should there be a UK republic declared, then the British taxpayer may have to buy Buckingham Palace as it may (in law) be the Queen's own property.
And of course, that is presuming the UK would- after many hundreds of years- become a republic instead of "Democratic Republic" which is not a republic (even though the Swedish meatball seems top think it is... but then he denies Sweden to be a monarchy).
I would "nationalize" whatever property I wanted, seeing the subjects of the monarchies have paid for the land over the years.
Leave the monarchy a castle and maybe a cottage on the coast.