I think you will find museums, as well as most institutions in the USA,
are more conservative than in other countries because we have to beg door
to door on an individual basis rather than facing the press (which can be
brutal in the UK I am told) and the governmental bureaucracy as
professionals do in those places where the preservation and transmission
of culture is a function of the government.  Not only do we have the press
and a notoriously fickle government that is fragmented into local, state
and national levels, but any civic organization or gang of nuts can make
our lives hellish.  We simply don't dare to take the chances.  If they had
hung an I. M. Pei pyramid on the front of the Smithsonian Castle building
I am sure some reactionaries would have formed death-squads to hunt down
the perpetraitors.