Having gotten his start in silent films, Hitchcock developed a genius for telling stories visually. He liked to remind critics that "in other words, we don't have pages to fill, or pages from a typewriter to fill, we have a rectangular screen in a movie theater." (Source)
Think about the first few minutes of Rear Window: the camera pans around Jeff's apartment and looks out at his neighbors just like our eyes would, letting us know that he's a (1) award-winning photographer (2) who got into a racetrack accident and is recuperating (3) during a heat wave, which (4) is making the neighbors keep their windows open so we can see them going about their (5) pretty ordinary lives. All of that without a word of dialogue.
Rear Window is one of Hitchcock's most visual films. It's about watching. He keeps the camera at Jeff's eye level, so everything we see we see from his perspective; if he can't see something, neither can we. Hitchcock never leaves that camera view except to show us Jeff's reactions. We are totally identified with Jeff's POV, never leaving his apartment and feeling as trapped as he does. When Thorwald realizes he's being watched and suddenly looks up at Jeff—up at us—it's terrifying.
We've been found out.
Keeping the POV so limited was a pretty bold cinematic choice that could only have been successful in the hands of a director confident in his ability to use images to tell the story.