Buck house isnt all that impressive i think many people only go there to see the changing of the guards etc. and the fact that the Queen lives there.I think if the Queen didn't live there it wouldn't draw any more tourists than any other stately home.Hampton Court Palace is far more interesting ( if you take the Queen out of the equation, in fact it gets far more visitors than buck house even with the queen)
Versailles on the other hand is another kettle of fish and visited for other reasons( one of which is, it is really most beautiful) the same as the most visited palace in europe which i believe is the Alhambra
Windsor Castle is another venue that attracts lots of Tourists,the Queen stays there often especially during the flat Horse racing season,her standard flies on the Tower when she's there,when she is you cannot move for tourists.
AS you said earlier,our Island is one of tradition and part of our make up and the tradition of the Monarchy is an important part of it.