If you consider the question of the visitor experience looking at the Crown
Jewels, the main thing seems to be not just "been there, done that" but also
being able to see the REAL THING.  However, unless you're an expert on gems
and regalia, there's only so long you can stare at the stuff before you're
ready to move on.  How long does the average tourist have to see the Kohinoor
to understand how large it is?  Since they can't do anything beyond looking
(no "hands-on" experiences!) there isn't much point in sticking around when
they still have the rest of the Tower to see.  However I agree that they should
have the option of standing longer if they want to see more.
 
Truthfully the only thing I really remember from the Crown Jewel room when I
visited (when I was 13?)was that they hung confiscated camera film on the sign
that told you it was absolutely forbidden to take pictures.  The rolls of film
had been exposed, pulled out of the canisters and strung up (like the heads of
traitors put on pikes?)  I came away with a sense of the intense security that
surrounded the jewels which emphasized that they were the real thing!  Whisking
people through on moving walkways would probably add to that.  (Rather like the
tour of FBI headquarters in Washington DC.  Very brisk and businesslike, and
you can't even go to the restroom without an escort.)