What varies is whether only you do the processing yourself or instead trust it to a recipe concocted by an engineer in the manufacturing firm who has never seen the image to which you're applying it. I can see times when one might want to do the latter--e.g., a photographer who has to produce a large number of images very quickly. However, that's expediency, not virtue.
Re processing in the B&W wet darkroom age: there was lots of it; it was just much harder and vastly less flexible.
I think you can actually find online the chart Adams drew showing how he wanted to process Moonrise Hernandez, but I don't recall where I found it.