Most police departments use Glocks and they all carry their Glock with one in the pipe. I have a Glock 23 and I always carry with one in the chamber. I always carry with one in the chamber, regardless of which pistol I'm carrying. Otherwise, I'm just carrying a couple of pounds of deadweight metal. When it comes to semi autos, it's more about the holster than it is about the weapon.
And stories of cops 'accidentally' discharging their pistols aren't exactly rare.