People who kill with guns do not care how loud the shot is. They know that by the time even the cops get there, they will be gone from the scene. They also know that no one is going to go rushing to the sound of a gunshot, they also know many people are scared of hearing a gunshot. Movies exaggerate how silent a suppressed firearm is.
Another important point is that houses are very good suppressors/silencers.
Think of the volume of a silencer. Think of the volume of a house.
The sound of a gunshot from the outside of a house, is much less than the sound of a gun with a suppressor/silencer.