The "wasting time" is literally adding three spoons of stuff to flour. (Two for me since I use a full package of baking powder.) It's literally in the 30 seconds range. If you were doing it a lot, you could even pre-mix them in those 30 seconds, and have enough for as many batches as you cared. It's a pretty weird micro-optimization.
You don't learn about how the ingredients work by making one thing from a recipe, but you do if you make a bunch of related things from similar ingredients. On the bread / cake spectrum, one learns to pretty reliably distinguish between things based on leavening agent and if they contain eggs.
Also, I wouldn't say that most above average home cook actually has much interest in cooking. But the average J. Kenji Lopez-Alt fan does. Most people cook because they need to eat. What I'm calling "interest" I'm imagining people where it's at least a hobby -- there's active effort in improving one's understanding of it and technique.