>IMHO managers should be giving continuous feedback
That would be great, however it is not always possible. Your manager may not be closely involved in your work, so for meaningful feedback they must bring focus from somewhere else. When calendar is packed with all sorts of meetings, it is easier to reserve dedicated time slot for you and guarantee that you will get all the attention this way. You may have never encountered a good manager, but they do exist. When I met one, I have got a massive decade long push in my career because of what I learned on those 1:1s.
