Dealers stock what sells, and for most it's the (new) M&P's, XD's , Glocks etc.
There's nothing wrong with plastic guns, I just don't particularly care for them. The Glock, XD, M&P's and others are reliable, durable guns that will outlast 99.9% of the shooters that buy them. The poly guns can go 80-100,000 rounds before anything major has to be changed out, besides recoil springs. The average buyer picks out a Glock 19, or XD, etc. and puts a few boxes through it and it sits in the nightstand or gets carried. Even most LEO's who carry the plastic guns don't put near enough through them to worry about wearing them out.
The age of the full size "duty revolver" is over, and most of them get sold to wheelgun enthusiasts. The days when a 6" 586 was a first-line choice for a HD or range gun are over. I still recall my Dad buying his 6" 586 and 2.5" 66 brand new in 1989 and at the time these were top choices for defensive and recreational handguns. If you went to a gun shop in the 80's the guy behind the counter would still show you new full size wheelguns that WEREN'T "collectible" yet
The plastic wondernines like the Glock 17 were still brand new and had not gained a foot hold in the market yet. Now, in 2012 when me and Dad take the 586 (or any of our numerous revolvers) to the range most of the firing line looks at us like we're shooting a flintlock