I see that, as usual, the topic has drifted from how to dress in the presence of royalty, to royalty in general and the intrinsic value of having it at all. Not living there, or even having visited, I am not at all qualified to debate costs, culture, pedigree or system of government....

However, because OF the long and complex history of Britain,(with some of my own family having roots there) I am in awe of the scenery, architecture, pageantry and cultural eccentricities. Genuine 'pubs' with local ales! I have had various folk bring me bottled samples, and have savored some amazing brews... on tap could be even better.
I would love to BE a tourist for a few months sometime and just walk in some of the places I have seen images of.... the famous and the obscure. If that means keeping those palaces, stately homes, gardens and monuments...etc. 'available', I would hope that it continues to be profitable AS tourist draws.
   I often 'drive' around England or Scotland in Google Earth just to see places mentioned in folks song and legend.... and in old British TV shows. I believe that Britain has been documented better than any place on earth.
I 'might' enjoy a live show of changing of the guard, but there are countless videos & images better than I'd likely get. I'd rather explore the art in some of the 'open' homes and take in the not-so-common views of the areas they are situated in.

Whatever the relationship is of "Constitutional monarchy" to the values of having the ambiance available, I hope it is maintained. If I never manage get there, I can still enjoy the place(s) in other ways.