Two factors here: the show was only a modest hit the first time, and didn't consistently sell out. It always alienated the crowd looking for traditional musical comedy fare. The revival wasn't stellar at the Roundabout (to put it mildly), but it reintroduced the show. It isn't everyone's favorite. The die-hards got in the first 3-4 months.
And then there's the Doyle-i-fication. Coming only a season after SWEENEY might be a turn-off to people who would be comfortable with the concept once, but find it cloying twice. Full disclosure: put me in that cateogry. As much as I tried to love it, I wanted to see the fully-played scenes -- I wanted to see a seduction,Robt and April in bed, not two clothed people leaning on a piano. It all became so slick and so minimal, I just missed the glass and steel edge, and yes, Mr. Tunick's sound.
I'm ready for the band to go back in the pit and stay there.
"I'm a comedian, but in my spare time, things bother me." Garry Shandling