He never liked to leave his office during working hours. He wore the same type of suit and tie so that he didn't have to think about clothes. He took the same suites in hotels around the world, so that he knew where he was, felt comfortable, safe. He controlled his films in the same way. Trained as an artist, he drew the film before filming.
Film is a visual medium after all.
Just as an artist collects fruit or models to paint, Hitchcock collected actors. I think the latter is the case. To Hitchcock, actors represented a style of person, in the way that buildings represented a style of architecture. A balanced and directed combination of elements result in a whole vision. To Hitchcock, the actors were part of both the image, the story, and the subtext.