Why does this get repeated so much

Because of the longer feedback loops. If you aren’t an experienced baker, you might not notice that the hydration is off, or that you’re not building enough strength in your dough, or that the temperature will cause the dough to rise slower than normal, and then you’re left asking why your loaf didn’t rise as much as you’d like, why the end result is dense, why the dough stuck to the pan instead of cleanly releasing, etc.

Once you’re experienced you’ll know when you need to add more water, when you’ll need to adjust times, whether the dough is too sticky, whether you’re tearing the gluten strands too much, whether your finished loaf is going to be more or less sour than you prefer, what adjustments should be made with the new flour you’re working with, etc.

But until you know how each step feeds into the next, being unable to taste the steps in between makes it a lot harder to learn quickly, and requires a longer working memory to connect how you handled the dough during an autolyse versus how the bread loaf turned out hours later out of the oven, and eventually learn the lessons of smell, touch, feel that aren’t easy to learn from written recipes.