Same with the public shelters in my area — mostly pit bull mixes or elderly dogs (often in pairs) surrendered when the owner passes away. Seems to be a more varied selection with private rescue organizations.
The inner city and country bumpkin losers who want pit bulls don't want to pay to have them spayed.
In our area (CT) there is a private group that takes failed hunting dogs from the Carolinas and brings them up this way to be adopted.
We have one of those dogs—part chocolate lab, part hound dog—terrified of gun shots, firecrackers even thunder—kinda obvious why he flunked hunting school.
He is a very friendly and loving pet—just what we wanted.