I've noticed that many older lens have just hard f-stops for lens (2, 2.8, etc). However, since the aperture wheel for some is continuous you can "stop" are some arbitrary point and shoot. From my post: How did photographers get the exposure right back in the day with only full-stop increments?, people can work with hard stops and fix at most +/- 2/3 EV later in post.
Assuming that's the case, what was the motivation behind creating 1/2 and later 1/3 f-stop lens? I understand that photographs don't need that much precision since we are using f-stops and not t-stops, referenced below. From that and my above example, it seems that 1/2 and 1/3 stops are nice extras? Isn't it enough to have a camera body that has 1/3 stops for shutter speed and ISO but hard stop for lens or is it a requirement that all factors of the light triangle must have 1/3 stops for aperture/shutter priority and auto? Related note, have we stopped at 1/3 stops or are lens makers going to have 1/4, 1/5 or some other smaller value for moving between stops?
EDIT: I am ignoring depth of field as f/stops do control that and I'm specifically focusing on getting the right exposure.