Nikkwong

Yes, that was what I was getting at in my first response, but I didn't want to give the forum a lecture on excellence and aesthetics in algorithms if you could do with less. Thank you for your detailed response, I completely agree with you.
Smart Mode is the layman's aid for tracing, but it is certainly not the tool for aesthetes or professionals. I prefer to draw curves myself, as I am trained now, and thus also know that the fewer nodes, the better. Actually, creating perfect aesthetic curves quickly and effortlessly is not straightforward, and that is precisely what the curvature tool assists with.
Smart Mode is for one specific need, I hope Serif does not think it also covers the other(s).
Smart Nodes in Affinity Designer: The use of Smart Nodes tends to create curves that are smooth and require less tweaking, which can be particularly useful for designers who prefer a more streamlined workflow. The automatic adjustments of curves can lead to a more efficient design process but might sometimes offer less control for intricate curve manipulation. Affinity Designer uses an algorithm for its Smart Nodes, which are designed to simplify the process of creating and editing curves. When you manipulate a Smart Node, the software automatically adjusts the adjoining curves to maintain a smooth and natural transition. The algorithm prioritizes ease of use and efficiency, aiming to reduce the need for manual adjustments of Bezier handles.
Curvature Tool in Illustrator: With the Curvature Tool, the aesthetic outcome is often characterized by very smooth and flowing lines. This tool is particularly adept at creating organic shapes and smooth transitions in paths. The Curvature Tool provides a balance between simplicity and control, allowing for the creation of complex curves with fewer adjustments. Adobe Illustrator's Curvature Tool algorithm is centered around intuitively creating and adjusting curves with minimal control points. It automatically generates and adjusts Bezier curves as you add points to a path, focusing on creating smooth, flowing curves that naturally progress through each point. The tool is designed to predict and implement the most aesthetically pleasing curve through the points you define, reducing the complexity of traditional Bezier curve manipulation.

Thank you for the kind and thoughtful responses. I would still like to push back that the smart mode (or smart nodes) are not the same thing—the curvature tool in Illustrator produces curves that have perfect curvature continuity. You can see this if you analyze the continuity of the curves that are created with the curvature tool. There is only one solvable position of handles for a given position of path points on a given curve. The smart nodes does not work in this fashion—I'm not entirely sure how it determines where to place handles for a given set of path points, but the result ends up being less aesthetically pleasing and requires more manual positioning, IMO. Thank you for the discussion and consideration. 

Thank you for the kind and thoughtful responses. I would still like to push back that the smart mode (or smart nodes) are not the same thing—the curvature tool in Illustrator produces curves that have perfect curvature continuity. You can see this if you analyze the continuity of the curves that are created with the curvature tool. There is only one solvable position of handles for a given position of path points on a given curve. The smart nodes does not work in this fashion—I'm not entirely sure how it determines where to place handles for a given set of path points, but the result ends up being less aesthetically pleasing and requires more manual positioning, IMO. Thank you for the discussion and consideration.