Above is pictured a Beretta I owned, on it is a Survival Consultants International WOR4 rail.
Every so often someone pushes the bridge rail for pistols as a new invention. Mounting an optic on the fixed rail is easier on the optic, and the bridge rail does not require permanent modifications to the gun.
Then come the downsides. You end up with a pistol nearly impossible to holster, unweildy and sometimes awkward to manipulate. There are several very major reasons why you don’t see many people use bridge rails on pistols. Outside of competition race guns and toys, they are just not practical.