When I was visiting Tsarskoe Selo, I had to insist that my tour include the Alexander Palace. The company wasn't really interested, and didn't have the "script" for the AP, so they were reluctant to include it. I wonder if the museums "tip" the tour guides for the numbers of people they bring, and the AP doesn't have the resources to "encourage" the tour guides to bring people there?
Clearly, in its current state and without including any of the Parade rooms on display, the tour of the AP is only of interest to true N&A fans. Once the palace is restored, it will hopefully begin to attract crowds.
BobG