I'm an American, and I'm pretty sure I have Asperger's, and I have no particular fondness for the British monarchy, or monarchs in general. In fact, I think it would be kind of cool to see it disappear in my lifetime.
Anyway, I don't believe it's simply about "tourists," for at the end of the day, it's the British populace itself that loves its queen. Oh, I realize many aspie Briton's here see the needlessness of it all, but I think, on the whole, most Britons either love their queen, or simply accept it as that which is.
Even Britons who aren't enthralled with the throne would not, deep, deep down, want to see it disappear. Just my observation of Britons, though I can be wrong. I think most of them either love, or cherish, or simply accept their queen, (as much as the sky is blue and the grass is green, it's a staple of their lives).
Besides, how can you have a United Kingdom without a reigning monarch? But if you get a chance, look up the song "Elizabeth Reigns" by Ringo Starr. Ringo has openly stated that he feels once Elizabeth II dies, the monarchy should end.
(That said, I do hope Elizabeth II makes it another couple years so she can surpass Queen Victoria as longest-reigning monarch of Great Britain.)