Alas we are suffering the same malaise over here in the West End

I guess in a large part its due to the high costs involved. The cost to the public to see a show and the cost of putting a show on to start with. Producers want a 'star name' to help publicise the show and put 'bums on seats'. Yet I don't think it helps the potential longevity of a show especially if the name isn't up to the part, it can do more harm than good.
Chicago here seems to be surviving largely on putting names into the show in various roles and using that to pull people in. Of course it can have the opposite effect if you don't like that person anyway!
Those of us on these and other theatre boards are the minority though of the audience, those who love theatre and will see a show because they love the actual show. Or perhaps see a show because a favourite performer is in that show . . . but that performer is only known in theatre-going circles.
In England we also have a lack of opportunities on light entertainment and chat shows for showing off new shows. At one time, getting on for 10 years ago now I guess, we regularly saw clips from new shows on certain shows. Publicity is often limited to posters on the tube and on buses in London and doesn't stray further afield.
We are at last getting 'The Producers' over here, but again with possibly stunt casting, Lee Evans and Richard Dreyfuss are, to my knowledge, not known for their singing! But at least RD is an actor!
"Well we can't all come and go by bubble"