This article is from the NYPD Blue FAQ, by Dave Chapman, Alan Sepinwall and Jeff Knapp with numerous contributions by others.
Well, yeah. But whether we "hard-core" fans want to admit it
or not, most of the show's viewers tune in to watch Jimmy
Smits and Dennis Franz, and they'd be annoyed if they tuned in
to an hour of the Gordon Clapp Show.
Some of Steven Bochco's series (Hill Street Blues, LA Law)
have been ensembles; others (Doogie Howser, Civil Wars,
Hooperman) have been vehicles for one or two performers. NYPD
Blue happens to be the latter. You may not always like it
(and, as a fan of James McDaniel & Co., I (and Alan, too!)
don't), but it's a situation that's not likely to change