You can still have chemistry on screen without getting on with the person. But it just makes your job a lot easier if you don't have to gird your loins, if that's not quite the right phrase, every time you're going to do a scene with that person.
Very few pilots even know how to read Morse code anymore. But if a pilot could read Morse code, he could tell which beacon he was approaching by the code that was flashing from it.