I know I had to eat a lot more when I was a novice because overload events were more frequent. I've seen the same in others. I welcome other opinions on this matter but my guess is that we get more efficient at turning over calories and protein, have a higher work capacity, and are less sensitive to weight fluctuations. If you look at advanced lifters they are typically settled into a weight class, improving very slowly, and generally at a reasonably high calorie level but maybe not so much to the point of inducing excess weight gain relatively speaking.