Working with Chaplin was very amusing and strange. His films are so funny but working with him I found him to be a very serious man. Whereas the films of Hitchcock are macabre he could be a very funny man to work with always telling jokes and holding court. Of course when I worked with Charlie he was getting older.
People could rationally decide that prolonged relationships take up too much time and effort and that they'd much rather do other kinds of things. But most people are afraid of rejection.