This is not a dumb question, just a good observation.
A single actions of that particular time period design(Colt) usually just has a grove cut into the back strap as a rear sight. Earlier muzzle loader pistols had the rear sight grove in the hammer, so once you pull the trigger, you loose your rear sight.
Single action are available with rears sights, but modern reproductions of older firerams tend to be more or less time period correct in their design and functions. Personaly I like the Ruger Bisley single action with the longer grip frame and adjustable sights. The Colt or Ruger designed single action grips are just too small for my hands